Dat RAM. Do what you want, but the boy scout in me would much rather have one 4GB stick to leave room for upgrading. You can get a single 1600MHz stick for as low as $18 and the price goes up as the heat syncs get prettier. Make sure to look at the timing. EX: 9-9-9-24. Lower numbers are better. I'm sure that RAM you have picked out is gonna be pretty schweet but just make sure they're not selling the word "game". You want to look for RAM with the fastest MHz and lowest timing in your budget. RAM is pretty much RAM regardless of brand. It's kind of hard to get wrong. You'll see some that looks pretty good but then only have one review of one egg that says "only showed up as 1333." ---It kills me because it's always their freaking motherboard.
Also make sure that PSU you've got has either an 8-pin or 2 4-pins. I know some mobos only have 4-pin connectors, so I assume there are some power supplies out there that only do too.
Your GPU also might take 2 6-pins. I really don't know. That's one of the few NewEgg mysteries that I never figured out. I can never find out how many 6-pins a GPU takes. Chances are you'll have at least 2 on the PSU, but if 1 GPU does take two then you're going to need at least 4 to crossfire in the future. I ran into the same problem.
Other than that it looks good. Really good.
Oh, and yes, if you got a 6770 right now then the graphics wouldn't crossfire with the processor's graphics and that thing alone wouldn't look as good as the A8 + 6670.