Hi Kriffith, I went for the G.skill PC3-12800 kit as I need or wanted a 4Gb kit for gaming and in a 2x2Gb configuration. The PC3-12800 looks well suited to this board and should achieve PC3-14400 speeds (1800MHz), as well as the 4Gb kit being £14 CHEAPER than the 2Gb kit to me this was an easy decision.

As the QX9650 has an unlocked multiplier as stock PC3-12800 speeds 1600Mhz using a 400Mhz FSB and a multiplier of 10 will give you 4Ghz at your CPU. If you raise the FSB for faster memory speed remember that you may need to reduce the multiplier.