As a die hard Intel fan I voted the AMD option
, it's true, at present AMD eats Intel for gaming platforms.
DDR 500 will be beneficial if you intend to oc your cpu, but the DDR400 will run things just fine, with a little extra voltage it will keep pace with the oc'd cpu, you'll just need to find the best divider.
I don't know about pricing where you are but I'd look at a better video card if your finances allow say 7800GT or a 7900 series, the 7600 is kinda "old hat" now.
Good luck with your build