DarrenCT

off the top of my head, i think it is the s4 6spd.

TheBrit

Off the line 0-62 times, S4 6spd as you say (but not by a lot). Not sure about 50-100 times, the S4 would make a good go at that too. I'd say 100-150 would have to be the S8, which probably would have the fastest 0-100 and 0-150 times too.

S6greytness

I couldn't find it with a quick search. But don't forget the A8 W12.....

Stealth4

With about $2000 for a chip and exhaust the S4 would have no problem rolling with an S8 at any speed. But stock the S6/S8 would be faster at higher speeds and probably equal at 0-60, perhaps slightly slower (depends on driver).
Overall the quickest audi is the RS4 (Germany, england)

Singletrack

RS4, soon to be the RS6 though.

Singletrack

They tested them at 5.4/5.5 0-60 in some magazines.

-st

Bollinger

RS4 isn't in production

Singletrack

Sorry, read "production cars" ... it is not in production anymore.

TheBrit

And not technically an Audi either...

Singletrack

Yes it is. Audi sold it, so what if another tuner worked on the engine.