I have 2x2 gb of corsair xms2 ddr2 ram lying around. Its about 1.5 years old but its BNIB. I could save on that. DDR3 is pricey too, how about getting 2gb ddr3 instead of 4? Would I notice a big difference?
Another solution u could buy mobo that can support both DDR2 and DDR3, but I don't know how would any of these perform during the OCing. Like this MSI 790GX-8D for example.