I feel like the 4gb one is a little bit of bs. Most cards of that nature will have a hard time even using three quarters of a gig of vram because the cores in the video cards are so slow. Anything above 1gb would be overkill. I would try to hold out and get a 7770 or a gtx 650/ti. If you can get a little more money, I would recommend the 7850 or 7790, those would be your best options for future proofing.