I dunno what card derb is referring 2.
I have researched this extensively before reading this thread. The most stable and OC'able 560ti out currently is the MSI twin...They sell a card called the Hawk, which uses a newer version of their heatsink. Its not really worth the extra $20-30. All 560 ti's with decent cooling easily OC to 950+mhz
Keep in mind that a new 560 ti comes out within a month or so. If you can wait for that, I would. It will have i think 448 cuda cores instead of the current 384. It is predicted to use more power so thats something to think about if you have a weak psu. More importantly I think the new 560 ti will fix some of the minor yet annoying bugs the ti currently suffers from, although that's just a guess.
If you cant wait, or cant commit a lot of power to your gpu, then get the MSI twin frozr II from newegg. Its now the winner of 2x customer choice award and for good reason. If your really into the epic warranty thing, EVGA does offer 2 560 ti's, get the superclocked DS one, because it has a sweet cooling solution, looks awesome and is pretty stable.