Here is a test in Auto Zeitung. I have scanned it.
http://hem.bredband.net/staszc/Audi/tidn/S4-M31.jpg
http://hem.bredband.net/staszc/Audi/tidn/S4-M3-3.jpg
http://hem.bredband.net/staszc/Audi/tidn/S4-M3.jpg
http://hem.bredband.net/staszc/Audi/tidn/S4-M3-2.jpg
Finally!
What amazes me most is that the S4 beats the M3 in acceleration! Although it is heaveier, has four doors, a V8 and Quattro....