An Audi S5? If you're really thinking about going with a 335i (which is a great car) you owe it to yourself to at least drive the Audi. I drove one in Annapolis a couple weeks ago and it's a much better car than the S4, mostly due to the engine being behind the front axle, which the quattro system has finally figured out...

[end unrequested opinion] ; )

Good luck, they are all great cars, pretty much can't go wrong!