RAM: ddr2 800 or 1066? i know that the processor i am getting won't recieve any benefit from 1066, however i am also looking at future upgrades, and eventually if i get one of amd's quads, the benefit from 1066 will be present. that said, ddr2 800 is cheaper, so it is likely 4 gigs of 800 vs 2 gigs of 1066
after that question, if i get ddr2 800 - 2x2gigs or 4x1gig - the 4x1gig would have better timings, but would it be a noticeable improvement? i don't know anything about overclocking, however i might learn how to once this thing is up and running
Motherboard: AMD 790GX vs 790FX vs 780G vs 790X chipset: part of me wants crossfire capability, even though i wouldn't need a second card for a long while, another part of me wants more than 2 pci slots, in case the 4870 ends up blocking one, i have a TV card i'll be taking from my old computer, and a second slot for my next question. also is the difference between SB600 and SB750 significant?
Go with the 2x2 GB DDR2 800 RAM 1.8v tight timings. Uses less power, room for expansion, usually cheaper.
Run the onboard sound first, you can always add a sound card later if it isn't up to snuff.
I'm not real good with AMD mobos, but i'd seriously consider this one Foxconn 790GX http://www.newegg.com/Product/Product.aspx?Item=N82E168...
that was one of the 4 or 5 motherboards I had my eye on
another question: as far as the voltage on the ram goes, what advantage does 1.8v have over 2.1v besides power usage? is it faster/slower/etc? what would be good timings to look for on ram meeting your criteria?