Whelp getting a little tired of the 660 now, just isn't quite cutting it anymore. Its time to upgrade. My choices are sliing the 660's or getting a 770. SLI is a buggy ordeal which steers me away so I assume I should go with a 770. But how much vram should I get? Is 2gb still enough or should I get 4? I run two displays (not exactly 1080p, one is 900p and the other is 720p).