My first time building a PC - Upgrading from a 2007 2.2ghz Macbook Pro. I'm looking to see a good improvement over my MBP, gaming wise. I play WoW, Fallout 3, SCII, and D3 when they're out. Might get Red Alert 3, Bioshock, COD4.
ASUS P5Q Pro ATX Intel Motherboard
The 750w would be fine for crossfired 4870s or if you replace your 4870 with a 4870x2. The Western Digital 640GB hard drive is faster then the 500GB one and is only about $5 more. You can get a better cooler then that, check here for reviews of both cooling and quiet. The Zalman isn't in the top ten for either. http://www.frostytech.com/top5heatsinks.cfm
Good build, solid.