I would like to add to Shantei's post and I can say that even without knowing if you'll be overclocking or not, I can say that you'd be better off with a 790FX chipset if you're going to stick with the 6400+ X2 or a P45/X38 if you're going Intel. http://www.newegg.com/Product/Produc...82E16813130136
The 790 FX, P45 and X38 all support Crossfire.
to make good chipsets, but either they got a hell of a lot worse, or AMD and Intel have got better. Nvidia's chipset offering can simply not stand up to what AMD and Intel have to offer in any way, that is the reason why SLI is so closed. AMD have the 790 FX, which is mature and proven, and it's only going to get better when it's paired with SB750, whilst Intel also have a strong lineup with the P45 and X38, both being excellent performers.
And the 9800GTX is pretty much obsolete now that the HD 4800 is released, in fact most of Nvidia's cards are obsolete now that RV770 is here. The HD 4870 is even faster than the GTX 260 for $300. It even beats the GTX 280 in some benches: http://www.newegg.com/Product/Produc...nd&Order=PRICE
The RAM you selected is not worth it at that price, get some cheaper 1066: http://www.newegg.com/Product/Produc...82E16820231166