Whats your budget?
Watercooling can get a bit pricey, and if your gonna WC the videocards, then might as well WC the processor too!
Motherboard: If you are going to go SLI then totally get the nForce 680i. If you are planning to stay single card, then go with the Intel Bad Axe 2, for its guaranteed stability
Video: 8800GTS 320 you might have a bit of trouble with, its 320mb framebuffer causes some problem you can read about here. I'd bump up the video card to the 640mb edition.
CPU: Core 2 Duo all the way! Not even the high end one either, you can overclock an e6600 to beyond x6800 speeds. If you wait about a month longer you can snag a Q6600 quad core for a low price. Simply put, Intel has the performance crown right now and AMD is playing catch up