Hey guys, I am looking to get another car, and I am about tired of the immaturity and garbage from the Japanese tuning scene. It seems like rice everywhere I look! I am considering an Audi s4 (used) as another daily driver/weekend warrior, just wanted to get some feedbacl on them, like potential, reliability issues, and anything/everything else you guys can throw my way! I am just looking for something European this time around, thats reliable, something a $2100/month budget can afford! Any other models you guys suggest for a n00b to this? I am all-Jap when it comes to stats, so bare with me if you throw a chassis code or something at me and I get confused. Again, thanks you guys!  

The S4 is a great car, and makes a great daily driver. The B5 S4 had the twin turbo V6 and has the most tuning potential. Expect to replace the turbos if you find a used example that still has stock units. K04s are the easiest swap and can get you a pretty easy 400hp. you can of course go bigger turbos for even more power if you want.

later cars had V8s, which while very nice, don't have the potential for easy power like the B5. You can supercharge the V8 and you can have about 450hp.

there are tons of suspension, braking and visual mods out there that give great results.  

I own a 2002 S4 which is the best year. This is my third Audi --2 S4's and 1 A4 --All have been modified.
My current S4 has 50,000 miles on the original turbo's. If you are going to track the car, likely you will replace the stock turbo's at some point. These cars are infinitely tuneable and so far I have found them very reliable. I would stay away from the year 2000 as they did, and I did, have problems with their turbos. At the track, I have found that the rotors warp and they are expensive. If you are serious go Alcon or Brembo brakes --fronts only. Great all around car but if I was doing a lot of track time I would probably go to an M3. gOOD LUCK.