What video card should I get?

Ok so I've been looking for a new video card to run 1080 gaming on a single screen and I'm not sure what separates cards in performance. I'd like to buy the ATI Radeon 6950, but I wanted some opinions on this and if it's a good choice. Basically what's the best card for under 300 bucks.|||I'd get the 2gb 6950 which is like $265 i think, and unlock it so it has 6970-like performance.|||5870, GTX 570 or 560, 6870, and the 6950 you mentioned if you can, go for a GTX 580 or that new one, GTX 590!!! if you can afford it LOL i'd give you mad props for getting the 590 no joke GET THE 590 things a beast!.