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To begin with, I think you may find there are some fitment issues with the stock C5 wheels, calipers, etc. The C6 Z51 rotors are quite a bit larger in diameter than the C5 rotors:
C5 Rotor Specs (all):
Front (in/mm): 12.6 x 1.26 / 325 x 32
Rear (in/mm): 11.8 x 1 / 305 x 26
C6 Z51 Performance Package Rotor Specs:
Front (in/mm): 13.4 x 1.26 / 340 x 32
Rear (in/mm): 13 x 1 / 330 x 26
There may have been one or two people here who have tried this. If so, perhaps they will chime in and let you know of the problems they ran into.
Obviously, you don't have stock base C5 wheels -- are they C5 sized, Z06 size, or C6 size? I could easily be wrong, but I thought C6 rotors were too big to fit inside a base C5 wheel.