I'd recommend nvidia or evga gpu's, my build has a Evga 550 Ti. It's a hundred bucks, you can get it on newegg, and it honestly has all the power you need.
If you upgrade gpu's, it might bottleneck or probably will bottleneck your system. So, I recommend saving for a new, good, gigabyte board, the gpu I suggested, and a new cpu.
What kind of PSU do you have? Do you know?
Too lazy to look up your current processor specs, how many cores and what's the speed?
(Again, didn't read post so I have no clue if you give info on...) Your current video card?
Your motherboards specs?
And how about RAM?
Lol, sorry, I know, a lot to ask. But you don't want to buy a new GPU and for you to put it in, for there to be compatibility issues with the Motherboard, PSU, and CPU. As that happened with me, and it didn't turn out so good.
Mainly, you want a motherboard with at least PCI Express 2.0 (don't know if you have that)
Dual channel memory, and if you're going for AMD processors, I'd go for A AM3+ socket Motherboard.
Edit, if you have a am3 socket, (most likely do.) go on newegg.com and search for a AMD Athlon II X4 640 Propus 3.0GHz Socket AM3 95W. It's a quad core, 3.0GHz and it's AM3, and 95W.