C6 is way better than C5, but that's why C5 prices are so low. As a base for building a performance car, the C5 makes a lot of sense because the platform is strong and the modding community is so strong.
GM rocks when it comes to bargain performance. The Camaro is insanely good value. "A $55K Camaro is great value?" Uh, when it includes a ripping V-8 and one of the best chassis sold under $150K, yes. The C7 Corvette was of course not as good for bang:buck as the Camaro, but still stellar.
And now GM launches a McLaren competitor for 1/3 the money? Diggety.