I did a lot of reading on this before I got my sli 4GB 670's for 5760x1080. The only reason I got 4GB models is because I was doing SLI at that high res and going to keep this setup for hopefully 2-3 years. Not sure if your res will befefit from 4Gb but I'm sure there are a few scenarios where you could benefit from it today, no telling about the future though. I saw BF3 killing my 1 GB 560Ti Hawk's ram and didn't want to ever experience that again, so 4Gb for me!
Also, SLI doesn't add the ram... 2+2 is still 2GB of ram.
I went 670 because they're like 3-5% slower than 680, but overclock great to make more than that up, and cost a whole lot less, especially when you are going SLI. 680 doesn't make sense honestly.
If u plan to SLI, from what I hear stock 690 = stock 670SLI and
SLI 680 is a few % ahead of both. And you can get less expensive great oc 670's to perform like 680's.
So keep those in mind while you're making your decision
Edit: also, when I bought mine these were the prices:
Galaxy 680 GC 4GB $575+ $8 each, no rebate. Total cost for 2 = $1166
Galaxy 670 GC 4GB $440 - $20 rebate, free shipping. 2x = $880 minus rebates of $40 total is a final of = $840
I saved $326 for near identical performance. Then I sold both borderlands 2 steam cards for $80 total so I paid $760 lol.
Not to mention the galaxy 2 Gb models were only $10-20 less than 4Gb...
I assume prices have dropped since then too.Edited by V!v!d - 1/25/13 at 1:07pm