Years ago, at a concert in Ann Arbor, Commander Cody and his Lost Planet Airmen upstaged (in my wife's mind, not mine, though it was close) the Byrds (in their Sweetheart of the Rodeo days). And I remember an old Wolman Rink Schaeffer concert where the James Cotton Blues Band upstaged the original version of Blood Sweat and Tears. I'm going back a long way...
'they blew'em off the stage'
what concerts have you attended, where the warm up act blew the headliners away.....my examples...brownville station upstaging zz top to the point where people where chanting 'brownsville station!' during the littl ol' band from texas' set.....another..t.rex upstaging lynyrd skynyrd(yes there really was such a show), and the grass roots upstaging cream.