If you want a 670, the one to get is the Asus. While many non-reference cards add an improved cooler, few have a factory heavily modified PCB, with an efficient VRM design to produce low temperatures, improved voltage regulation circuitry, much better CHiL controller , specially binned chips and voltage control and monitoring support that you won't find on most other non-reference cards. Those are some of the reasons you'll see it get a 10.0 rating at techpowerup, something no other card has ever attained.
Also compare here with the 670's listed:
10.0 Rating Asus 670 TOPhttp://www.techpowerup.com/reviews/ASUS/GeForce_GTX_670_Direct_Cu_II/33.html
9.7 rating MSI Twin Frozr IVhttp://www.techpowerup.com/reviews/MSI/GTX_670_Power_Edition/33.html
9.6 Rating Zotac AMP 670http://www.techpowerup.com/reviews/Zotac/GeForce_GTX_670_Amp_Edition/33.html