You're better off getting a 680 at that price. The amount of RAM isn't all that important, as modern GPUs just tap into your system RAM as needed and it's cheap to go overboard on that.
For barely more, you can get the Gigabyte 680
with 2 games for $430 after the mail-in rebate. I'd recommend that, if you're dropping $400+ on a card. If you can't return this card/swap for a 680, then the 670's still a very high-end card, so no worries; but the premium price tag for the extra 2GB of RAM isn't worth it. However, the overclocked speed will make it perform almost like a 680.