Have you bought these parts? I question why you got a p67 board with an Ivy Bridge.
@topic - 600w would be plenty for a single card. For 2-way CF though, 750w would be really close to the edge, and seeing as you're also overclocking, that leaves little to no headroom left. The PSU will be working very hard.
I suggest an 850w. Also, any 80 plus certification would be good, Bronze,Silver,etc, the difference isn't really that big.