Think I'd go with the 670 at those prices, then in the future, like you say could SLI and it'll be even less
The more I think about it the moreits a good idea. the 670 is plenty of GPU power to run all games at high right? And when ill want to slii will buy a used 670 for 200$ and get the power of 1.5x~ gtx 680 for the same price!
Instead of the 680 I would go ahead and get the 770 if you can afford it and the extra power will keep your games maxed for quite a while
The 770 is not an option. It is grossly overpriced atm when the 600 series is on sale. 279,99 for a gtx 670 vs 449,99 for gtx 770 not worth it in my opinion.