That is slower than both the Q6600 and the 9950, and it's more expensive.
If I were him, I'd stick with the original 2x2GB DDR2 1066 kit he was originally going to buy, it's only $10 more.
I don't really recommend duals anymore as quads are available at such great prices and at decent clock speeds, the Phenom 9950 is an especially good deal now.
As for the DDR3, DDR2 is still so cheap nowadays and the CPUs he's looking at aren't going to benefit from it. It's going to come down in price still so it's be an easy upgrade in the future. And I don't think you really need i7.