Hey Klaus, If we were talking about R comps I'd agree with you to a point. But I was simply stating, a lot of the autocrossers are showing up with off brand chinese made tires or Falken 452's, Kumho 712, or Exclaim UHP's and they are all crap when it comes to performance. Obviously bought based on price. However Dunlop star specs, Bridgestone Potenza's, Eagle F1's etc are top notch street tires that perform way better than the other's mentioned and won't chunk nearly as easily as they are designed for this kind of thing. Plus the PAX factor will not be affected as they are street legal DOT tires. R comps and A comps for that matter may move you into a different PAX factor that negatively hurts your times.
So that said, tires a BIG first modification then suspension. Not to mention purchasing top notch street tires, is way less expensive than a coilover setup.
From a performance aspect, (given an experienced driver) stock car with r comps is faster than coilovers and crappy street tires. No doubt about it.
BMW 325I E30 Chumpcar Race Car
BMW 540iT M-Sport (New Family Hauler)
BMW 428i Maranello BMW company car