have a build on its way and its sort of a budget build but I have things to upgrade and my first card will be a GeForce 660 2GB. I was wondering if later if I wanted to setup SLI would the 3Gb version of the 670 or 680 I think it is work with it? or would I be better off leaving the 3gig to itself? Ive heard it both ways.
No it must be two of the same cards ie. 2 x 660 or two 670 for sli. You can have different cards (like a stock version and an OC version) but they need to be the same model.
You can however use the 660 as a dedicated PhysX card, but that would be a waste in my mind. Getting a second 660 to sli would be the best bet.