How good can you drive, and how good can the people you intend to compete with drive?
I've beaten Vipers, Z06s, BMWs, an Audi R8, a Ferarri 360 Modena, and a whole bunch of Camaros and Mustangs... I've also had my ass kicked by several mostly stock Miatas on street-tires.
I recently autocrossed an '05 BMW 330i that I honestly thought didn't handle as well as my Chevelle... but I was 3 seconds/lap slower than the guy who owns the car, so with a little more seat time and adapting to its understeer characteristics, I could probably have been faster in it than I would be in my Chevelle.
My car just has more adjustment that makes it easy to make the car adapt to me instead of me adapt to the car.