change the mobo to the asrock z77 extreme4 from newegg man, they are giving away free 2x4gb of 1600ghz pc3 12800 SDRAM with the purchase of the mobo at 134.99, everything else looks great, stick with the 750w, thats a good size and particular one, the sli 660's will be good, but maybe look into getting one 680 instead, it is a beast right now and you can always resort to SLI'ing it later on when technology advances instead of having to go to two different cards all together when the 660's become outdated.
EDIT: also that mobo is a beast, definitely the best one for you, on top of that free ram as a perk =)
Certainly, when throwing in 8GB of decent RAM, the Extreme 4 is a good deal. It's obviously a judgement call, whether it's worth paying a premium, for the quality, and BIOS/overclocking ability of the GD65. The GD65 is one I will consider, for an upcoming build.