I'm building my first gaming rig, but I cant decide about the graphics card.I already bought a gtx 670 2gb 2 days ago , but I'm worried about the Vram problem. I'm not planning to upgrade for the next 2 years.Do you recommend me to return the 2 gb one back and buy the 4gb version or SLI 2 x 2gb ? I want at least 60 fps in every game, especially metro 2033 , with tesselation, advanced DOF, and antialiasing(8xq or 8xMSAA+2x2SS) maxed out.I will try to overclock but not much.I will mod skyrim and everything.
There isn't any games that will require 4GB of Vram. To have that much you would have to have many monitors and run in very high resolution like 2560 x 1600 to get the use of the Vram.
If you want to run 60fps on everything then just start with the card you have and if you are not getting what you want then either get another 670 2 gb of Vram or get a 680 but of course send back the 670.
You try with what you have then it goes up from there. I hope this has help a little and good luck to you and those cards are very nice I think you will be impressed and it should handle any game thrown at it.
If you want more firepower then go SLI, not with more VRAM. Note that total VRAM for 2gb cards in SLI would still be 2gb but that would be way better than a single gtx 670 4gb. And as mentioned by others, VRAM will not be an issue unless you go multi-monitor setup.
VRAM does not add up when you SLI - just because you have 2 sets of 2GB 670's , the total VRAM will not be 4GB, it will stay as 2GB. As for METRO 2033, - the GTX 670 is benchmarked at about 50+ FPS average.