I would go for 670 as it can reach esily 680 stock clocks. You won't need that extra vram at this moment (and for at least 2 years) unless for heavy texture modding in Skyrim. Edit: oh, and you should crank up your cpu. your SB at stock clocks will botleneck dramatically the gpu (given my experience).

For card like GTX660 2GB is more than enough.

I have 🙂 its running at 3.8 now 🙂

I'd still recommend the 670! Ps. the Windforce's are awesome, my 460s are also by GB 😀