There's no Emmy for best performance by a megalomaniacal billionaire, but the Academy of Television Arts & Sciences should bestow one tonight upon Sumner Redstone, anyway. Redstone, 76, is the chipmunk-cheeked chairman of Viacom Inc. who last week engineered a $38 billion takeover of CBS. Wall Street was pleased about the proposed merger, but TV viewers should be ecstatic.

Why? Because for viewers who care about free, original entertainment seven nights a week, it's come to this: Now is the time to root for the big guys, the conglomerates, the mega-studios. Otherwise, we might someday be saying goodbye to prime-time programming as we know it.

Assuming the deal goes through, Viacom's takeover ensures that a once-cherished cultural institution, the CBS television network, will survive to be cherished for years to come. By combining with Viacom, CBS will get the kind of financial security blanket and multimedia razzle-dazzle it now lacks. That should keep high quality (or at least expensive) programs on its airwaves.

There's a downside, of course. The network, and its once preeminent news division, will become one more brick in Redstone's massive corporate edifice. By swallowing CBS, Viacom will be the parent of Paramount movie studio, Blockbuster video stores, cable networks such as MTV and Nickelodeon, a giant billboard company, a wealth of TV stations and more radio outlets than Marconi ever dreamed of. Those worried about the increasing concentration of media power in the hands of a corporate few are right to be concerned about the emergence of Big Media Brother.

But bigness (i.e. deep pockets) is exactly what CBS--and the other broadcast networks--need most these days. The fact is, big companies tend to make big profits, and it takes big profits to sustain strong TV networks. At the moment, the CBS network is not making money, despite being the most-watched on the air. Having a rich and powerful parent will be an absolute necessity if the network is to continue affording the likes of "60 Minutes" or "Touched by an Angel."

Running a broadcast network is a tough business, and it's getting tougher all the time. For starters, it's been evident for about two decades that many viewers regard the networks as Must Flee TV. Where once they commanded more than 90 percent of the TV audience during prime time, ABC, NBC, CBS and Fox collectively will be pleased to pull 50 percent when the fall season begins next week. The networks fell below that symbolic figure last season, the first time a majority of the nation's TV viewers preferred the choices on cable to those on the networks. That milestone might have escaped your attention, but rest assured advertisers were taking notes.

Much of this was inevitable, no matter what the networks aired. TV audiences have scattered like so much sand in a hurricane because their attentions have been diverted by dozens of alternatives. Fully 75 percent of all households have cable or satellite hookups (up from 20 percent in 1979). Long ago, the old Philco strained to pull in four or five channels; today, American TV viewers receive an average of--cue the Springsteen song--57 channels.

There's more. Technologies such as remote controls (now in 94 percent of households) and VCRs (90 percent) have enabled couch potatoes to tune out the networks with a flick of the wrist. No one knows what future technology will do to the networks, but it's unlikely it will help. As the Internet creeps into more and more homes, it becomes possible to deliver programming over the Web. Remember 500 channels? Think 5,000--or 5 million.

The networks bear some of the responsibility for their descent, of course. Too many lookalike sitcoms and too much all-around lousy programming have turned off some viewers. Too many commercials, reruns and annoying promotions for those crummy programs have driven away still more.

But for every misbegotten "Veronica's Closet," every reeking new Fox sitcom, every tired, made-for-TV slasher movie or trumped-up "newsmagazine," the networks remain TV's last great hope. Thanks to the fact that they can be seen in virtually every household in America (and thanks to the advertising dollars this attracts), they're still the only ones able to afford original, scripted entertainment, news programs and big-event broadcasts such as the Oscars seven nights a week.

Cable networks can't make that claim. Networks such as HBO and USA have gone into the business of producing original series--HBO's "Sopranos" could be the biggest winner at tonight's Emmy Awards--but no cable channel reaches enough viewers to underwrite the same number of programs, with the same production values, as the networks. In fact, discounting pro wrestling, pro football and "Rugrats," the biggest attractions on cable are reruns of recent network shows.

Indeed, despite its wandering viewers, network television in many respects is better today than ever. "ER," "Law & Order," "NYPD Blue," "Everybody Loves Raymond," "The Simpsons," "Frasier," and the recently canceled "Homicide: Life on the Street" surely rival the best programs from any other era. They surely rival much of what's playing at the movie theater right now.

The problem is that shows like these are becoming almost prohibitively expensive. A network-quality sitcom, even one with only semi-famous stars and second-rank writers, costs roughly $1.25 million per half-hour. A one-hour drama runs at least twice that. Last year, NBC stunned the industry when it agreed to pay Warner Bros. $13 million for each episode of "ER." NBC also pays Warner Bros. a $6 million license fee for every episode of "Friends."

Add to this the inevitable cost of failure. Last season, 36 new series debuted on the Big Four networks and the upstart WB and UPN networks; only 10 of those shows will be on the air again this season. Behind this casualty rate lies still another--the dozens and dozens of pilots the networks commission each year, most of which are never seen outside a studio screening room.

Alas, as the networks slowly crumble, so does their ability to sustain this highly inefficient system. Viewers already can see the cracks. The rise of prime-time "reality" shows--"Cops," etc.--illustrates the networks' growing weakness. The networks favor these shows, even though they tend to earn lower ratings than scripted series, because they can be produced quickly and cheaply, and aren't dependent on the whims and salary demands of temperamental superstars.

Reducing production costs is a first step toward self-sufficiency, but it alone won't solve the networks' larger problems. This year, NBC is the only network that will make a profit. Combined, the four largest broadcast networks aren't as profitable as any of the top 10 cable networks. This grim arithmetic prompted NBC president Bob Wright to suggest recently that NBC--venerable peacock and all--might be better off converting itself into a pay cable network.

A more rational approach, it seems, is to create larger, more integrated and more efficient multimedia companies with the networks at their heart. That's what News Corp. (the parent of 20th Century Fox film studio) did when it started the Fox network more than a decade ago, what Disney did when it bought ABC in 1996, and what Viacom is doing now. Eventually, NBC will have to do it, too.

Viacom sees the CBS network as the anchor store of a huge mall--one in which Viacom owns all the stores. With its still-popular shows, CBS will draw in people who can then be directed to Viacom's many smaller outlets--MTV, Nickelodeon, VH1, and so on. The process should work in reverse, too.

An even more important aspect is that Viacom can now bring Paramount and CBS together, linking up production (the studio) with distribution (the network). This means CBS will have a captive program supplier, which will enable it to better control its program costs. It also gives Paramount an unrivaled platform to launch new shows and keep them on the air long enough to collect enough episodes (usually about 100) to sell reruns to independent stations and cable networks, which is where the real profits are in today's TV world.

Further, Paramount could put some of its feature films on CBS after they've left theaters, while CBS could send reruns of its shows to Viacom's Nick at Nite or TV Land cable channels. In turn, MTV could help bring young viewers to CBS by supplying shows such as "Road Rules," or by promoting CBS's telecasts of the Grammys and the Super Bowl. And Nickelodeon's popular children's shows could make CBS a power again on Saturday mornings.

All of this would reduce the overall cost of running the network, expand audiences and attract more advertising revenue. Unless Redstone is uncommonly tightfisted, all of that money could be plowed back into more and better programs.

A small demonstration of the potential synergies between Viacom and CBS may come later this fall, when Viacom's VH1 channel airs the cable premiere of the CBS rock miniseries "Shake, Rattle & Roll" a few weeks after it appears on CBS.

The history of giant mergers teaches that synergy often works better on paper than in reality (Disney, for example, is still struggling to turn ABC around). But in a mega-media future, in a 5-million-channel world, it may be the only way to keep the humbled networks thriving. Once the gigantic management and regulatory issues raised by Viacom's takeover are sorted out, CBS's executives may be able to stop worrying about extinction and start solving a problem as old as TV itself: dreaming up a few programs people want to watch.

Paul Farhi, a reporter for The Post's Style section, writes about the television industry and pop culture.

CAPTION: Although cable television occasionally produces a critically acclaimed show such as "The Sopranos" (top left), only the networks can afford to churn out enough original programing--from "60 Minutes" to "Friends" to "ER"--to fill a prime-time schedule night after night.