I always believe getting a gpu with the best specs for its class is the best option. You'd be paying 5% more for up to 10% more performance, and that's until you overclock.
I assume also that you are talking specifically about EVGA's 670s? I am much more of a fan of the msi power edition if you can find it, the cooler is just a beast.http://www.tigerdirect.com/applications/searchtools/item-details.asp?EdpNo=3199441&SRCCODE=GOOGLEBASE&cm_mmc_o=VRqCjC7BBTkwCjCECjCE
You can find the gpu for $430 on newegg when it's in stock. The evga card is appropriate for people not looking to overclock further. Good luck!