Well, the 2gb version is for multi-monitors. If you play a with one monitor, 1gb should be fine, unless you are playing metro 2033, or games like that. The GTX 560 ti is great too. What games do you play? What is your set up? PSU, CPU, MB, RAM, etc.
ohh.....i c... i just have one 22inch monitor, and I think i'll be sticking with it for the rest of my student life..
mostly fps games... i'm planning to build a set-up, but i'm stuck in a dilemma between the gtx 560ti and HD 6950...although the 560 ti is like 30 pounds cheaper...