re: new video card

It all depends on the kind of gaming you plan on doing. My build is

AMD Athlon x4 640 3 GHz quad core processor
AMD Radeon HD 6850, 1 GB VRAM
4 GB DDR3 1600 MHz RAM

You don't need lots of RAM, 4 gigs will suffice. I recommend 6 but 4 will get you by pretty well unless you multitask tons at once at all times.

My build cost me $650 and I haven't run across something it can't run at max graphics. SC2 doesn't dip below 35 FPS. When I played Rift at max graphics I'd get ~60 FPS, except in towns and in rift events.. Those were about 20 FPS. But I built my rig in a way where it's easily upgradeable. Whenever I get some extra cash I am going to buy another 6850 and Xfire them together.

I've always been an Nvidia guy myself, but I've been very satisfied with my Radeon.