Above is a really useful link for that mobo and core 2 duo. I'm in the same boat, gonna buy a ASRock 775Dual-VSTA and an E6600, but I'm looking for RAM to upgrade from by current pitiful pc2100. Scroll down to the index for the whole article. Anandtech.com also has some other good articles on that mobo.
If you - and anyone else - who's heading for ASROCK + C2D + DDR2, then try ASROCK ConRoeXFire mainboard (see specs at ASROCK's website); if you're going PCIe instead of AGP, this one's a better choice for a few more bucks.