Great list of cars...That would be a tough choice for me. The Challenger and Camaro are overpriced at this point and very heavy. Although the V6 Camaro is getting very, very good reviews and its relatively cheap. We all know about the STi and EVO, no brainer there...good cars. I LOVE the Elise. I almost bought one about a month or so ago but just couldnt work out a decent deal on my trade. It's a fricken go-cart, not overly fast in a straight line, but handles like a dream. The S5 is awesome but VERY pricey. But it you want a luxury AWD drive car with great performance, you've nailed it in the S5. You know it's funny I dont know alot about the Mustangs, as popular as they are because my dad had several stangs and they were all garbage so I've stayed away from them. The new one's definitely look nice though.
My favorite is probably the 2005+ Vette. Man, what dont you get with that car? It looks awesome, actually looks very nice inside as well and the performance potential is off the charts. It's fairly pricey but not awful.
After the Vette, Id go with the Elise