S4 or RS4 .... I have some questions.

All,

After much shigrin (sp), I finally sold my old track car (2003 Evo note vids below for fun), and have decided to move on to something more 'adult'. I have been looking at S4's for some time, and have ridden in plenty around most courses in the SE US. Unfortunately, I am no guru when it comes to the intrigue detials of these fine machines.

First, this car will see VERY light track duty, but mostly will be a daily commuter for the wifey. The wife and I have decided to consolidate our rolling inventory down to one nice car, and my company machine. This opens the opportunity (and budget) to do something fun for both of us. The wife has been trying to get my to consider the Audi for some time, but I have never pulled the trigger due to the cars weight (I used to only buy sports car dedicated to track duty). Knowing this will see mstly street duty, I want this car to be nice to ride in, but still be competitive ont he track, should I consider a time trial here in the SE. However, I DON'T want to start another money pit, so I want to make sure what I buy will be 'capable' of doing either role with little or no modding.

That being said, my wife, loves the 2001 S4, which her brother has, but I am leaning toward a newer S4 because of warranty. I have even considered the RS4 as an option to feed my need, without having to do ANY mods to the car. What would be the advantages / disadvantages of going with a 2001, 2005, or a new RS4? What things should I really be weighing here? How many mods (suspension) are really avaiable for a car like the RS4 and how much do they really help a car of it' caliber?

Thanks in advance for your input, I would love to here testimony from folks with S4/RS4 doing the light track/daily duty at this time.