Ram: CORSAIR XMS3 DHX 4GB
On a current Intel platform, DDR3 brings no performance increase because of the limitations of the FSB. The bandwidth of the memory can never be higher than the FSB's frequency. For example, if the FSB is 400 (1600MHz QDR), that's 12.8GB/s of bandwidth, 12.8GB/s = DDR 800, therefore using DDR3 at a higher speed than DDR 800 would bring zero performance increases because the FSB is still the limiting factor. And the potential frequency of the FSB is not high enough to benefit from DDR3.
So my advice is stick with DDR2 800 or 1066.
When AMD's Phenom supports DDR3, and Intel's Nehalem is released, only then will you see the full benefits of high speed memory thanks to the IMC (Integrated Memory Controller) which can make use of all the bandwidth.
Buy DDR2 now, buy DDR3 when Phenom DDR3/Nehalem is released, by then the prices will have dropped as well.
This is a great deal ATM: http://www.newegg.com/Product/Produc...82E16820231166
I would recommend you spend no more than that on your memory.