[Perfectlap]

I had Kumho's on my old car and although they were certainly a bargain I'm not I would buy again. Something in the rubber compound lent itself to flat spotting. So for a passenger car it would be better but for a car where you will have to get on the brakes hard more frequently I'd spend the extra dough on Michelin Pilots or similar from Bridgestone.
I don't have a great deal of experience with Pirelli but their durability stood out to me as not being very good relative to what I've tried from Michelin, Toyo, Bridgestone, Dunlop. By the way that price your dealer quoted you is not good at all.

Tires really are not an area you should be cutting corners on when it comes to sports cars. Its maybe the most important maintenace item you will ever spend your money on. Check the tireRack.com they will ship the tires to a shop near your home and they offer discounts on mounting and balancing.