If you're that paranoid about getting a good OC'er, you should buy it used from a trustworthy OCN'er who will guarantee the clocks for you. Otherwise, it is a TOTAL crapshoot how high the card will OC, no matter what brand/model.
If you're not concerned about aesthetics (i.e. matching) and want the best cooling performance & the best chance of a high OC, I'd grab an evga FTW model. Of the non-voltage controlled 670's, these have shown to be one of the best OC'ers on AVERAGE, esp. with memory OC's. Also, putting a 'blower' style card in the bottom position is the best for cooling a SLI setup, wherein the upper card is always the issue. A blower cooler on the bottom means less hot air being sucked up by the upper card's cooler
A good way to tell how much SLi is going to help you is the simple GPU usage test. If you're consistently pegged out at 97-99% while gaming, that's a pretty solid sign that SLi is going to help you out
I can also testify that the WF3 is not that loud of a card at all. I mean, if you run it at 99% for awhile, you definitely can hear it and everything, but it's not an unpleasantly loud card by any stretch. It's nicely low-pitched rumble when the fans ramp up. Mine will do 1372/3546 on a modded (1.212V) bios, or like 1354/3546 on a regular bios (1.175V). But I have a particularly good one. And your top is particularly good ... most 670's tap out in the 1230-1300Mhz range on stock bios.Edited by brettjv - 2/26/13 at 10:14am