Well 2gb and a 6800 won't make much sense because I don't think you will be using more then 1 gig on the settings the 6800 will run smoothly. I'd get the 7800 and 2 gigs.
so for cpu what would be better? the 3700 or the x2 3800? i will be going almost everything...games, video editing, photoshop, web design, apps and documents etc.