Here's a video of a genuine '06 Audi RS4 running heads up against an '03 BMW E39 M5 with a Supersprint exhaust system courtesy of the M5Board. The M5 pretty much smokes the RS4, but I must say that the RS4 is a very attractive machine.

http://www.m5board.com/vbulletin/showthread.php?t=81728