Twenty thousand people showed up for the "Showdown" at the Capital Centre Saturday night and no one looked disappointed when they left.

"Capital Boogie Showdown" featured three acts, including the Average White Band, and the resulting sellout justified the move from the Washington Armory, site of last year's affair, to Largo where more people from a greater area could attend.

T-Connection opened the festivities, warming up the crowd for Slave, an outfit modeled loosely after Earth, Wind, and Fire but far less polished. Slave jumped and shouted through a powerful but not very distinctive set highlighted by a smoking percussion section and occasional flashy horn arrangements.

After some mild stage politicking by the WOL/Compared to What staffs, sponsors of the benefit event, and City Councilman Marion Barry, the Average White Band got the audience back to boogeying.

AWB's success lies in its superbly tight instrumentation and an ability to mimic, especially on ballads, vocal phrasings of top rhythm and blues artists. Their performance Saturday night proved the point. Prancing smoothly through a well-paced cross-section of their best known songs, AWB kept everyone cheering.

"Pick Up the Pieces" opened the set on an appropriately funky note and the Scotsmen's brand of blue-eyed soul shone during "Person to Person," "Work To Do," and other percussion/bass-oriented tunes. Hamish Stuart's and Alan Gorrie's crooning on slower numbers like "If I Ever Lose This Heaven" borrowed heavily from Marvin Gaye, Smokey Robinson and Curtis Mayfield. The band deviated slightly for a jazzy instrumental tribute to the late saxophonist Cannonball Adderly while the premiere of AWB's new single, "Get It Up For Love," featured Ben E. King on lead vocal and added even more soul to the proceedings.

The festival seating arrangement allowed anyone willing to risk the jammed floor area an opportunity to dance. And those filling the seats had no compunction about leaving their chairs to shake in the aisles.

The emphasis Saturday night was not so much on music as rhythm and none of the bands lacked for that. Except for a gate-crashing attempt that Prince George's County police said yesterday resulted in seven arrests, the party mood and considerable proceeds, part of which are to be donated to help area youth, made "Capital Boogie Showdown" quite a success.