thinking about ditching the M3 for a Quattro - but I think it would need new wheels and perhaps front spoiler - are there any big companies that do this ?

eg. for BMW, you'd look at Hartge or Racing Dynamics for example.

Who are the big names in Germany that do the wheels and body kits fo Audi's?

 

If you start with an 'S' or 'RS' version the car will be compleate. Then you can change the wheels to other RS model wheels. Miltek do the exhuasts and jabba sport will re-map and then the job is done

 

are there any sites you know with new shape A4 and A3 cars with different styling kits and wheels ?

Like this:
http://www.germancarfans.com/photos....ge/audi/1.html