This is a very bad time to build. Intel did a recall last month on the Sandy Bridge motherboard chipsets, and the replacements aren't going to be out until April:
http://www.anandtech.com/show/4142/i...-begins-recall
On top of that AMD's Bulldozer is going to be coming out "soon", which is the CPU where AMD is finally updating its CPU architecture to be comparable to Nephalim. The Phenom line isn't much more than a multi-core Athlon 64, which was OK when they were going against Core 2, but hasn't cut the mustard for a while now.
In short, wait until the Sandy Bridge chips are back on the market, and if you can, until the X68 are hitting the market. At worst it will drive down the prices of the hardware you're looking at. At best, AMD will have come out with their next gen CPUs and we'll have a price-war on our hands, which will mean you can get an awesome box for what you're looking at now.
As for power supplies, I'd recommend one of these:
http://www.newegg.com/Product/Produc...82E16817139006
And it comes in modular for if you're willing to pay an extra $50
http://www.newegg.com/Product/Produc...82E16817139016
The big deal about them is they have a unified +12V rail, with 60A of power on it. The +12V is what your video cards and CPUs run on. the 3.3V and 5V are for the fans, hard drives, and other powered peripherals, so unless you have the RAID of Doom, you don't really need that much on those lines. The low volt lines are easier to add amps too, so low end manufacturers tend to add most of their power there, to pad their numbers, which is how you end up with the 3D card makers having to recommend KW PSU's.
Went digging to confirm exactly what the power requirements are on 3D cards and SLI, and it looks like the 6 pin PCIe power hookups are rated for 75W, while the 8pin ones are rated for 150W, so you can use that to get the max expected power required by your 3D cards. For the CPU, I would start with it's TDP, and add some percentage margin. I'm thinking if the two 3D cards you're looking at have an 8+6 power pin config, then 720W on the 12V rail should be fine, but if it is an 8+8 pair, you will want 800W 12V power at least.