I am considering buying a project car for the occasional autocross and driving school. The car will also be used as a commuter, alternating with the Beast. I am also thinking about a convertible, even though they are not as rigid for driving events. I have a cap of around $40,000. I am considering the following cars:
I think I would go with either the e36 M3 or the C5. The M3 is a great car for autocrossing and track events but it may become a lot to maintain and repair. Now, the C5 is just a beast. Mods are readily available, there is a Chevy dealer everywhere you look and they are very cheap used. I personally would go with the C5. My freind races his about 6 times per year all over the East coast and has had no problem with it. With slicks and lowered suspension he ran a 1:02? at Lime Rock. That is very quick for a car they drive everyday. A track car is going to break, and Chevy has the definite advantage over BMW in this area in relation to parts and mods. I say go with the vette. Go with what you like best. Take them for a drive and see what you think.
I'd go with the M3 or 993 for the following reasons -
1. Both are a blast to drive.
2. Both have very good on track/autocross (I had a 993 for about 2 years and loved the autocrosss events held by PCA (Porsche Club of America).
3. Although not a factor you listed - these should hold their value better than the others when you decide to sell it (to buy that 360, of course! )
NSX - I wouldn't go with, my experience is insurance/maintenance is very high. My experience is it burns thru tires in about 10k miles.
Corvette - Friend has a Z06 Corvette and his experience is durability is very suspect (it spends a lot of time in the shop - good thing there ARE lots of Chevy dealers)
S2000 - Sounds like a good choice, but have no experience with this.