Right now the Asus P5W DH Deluxe is probably the best motherboard you can get for a Core 2 Duo. The ATI RD600 is supposed to be coming out in October. I'm going to buy one of those two. If you want to run SLI you'll probably have to wait a few months for the new nforce 590 boards to come out. This
has a good write-up on C2D mobos.