I have i7-2600k, Asus maximus IV extreme p67, ax1200w, h100, 8 g g.skill vengeance ram and 2x gtx 260 OC.
The problem i am having is that the mother board doesn't want to read the second card. I went in to the bios and saw it was only reading the 1st one but the the second one. I have a so removed it and put it into a difference computer and it works fine. I have undated the drivers for the gtx 260 and still nothing trying to have them SLI. (Btw whats a good card to upgrade to ether 2 good cards sli or one really good one)
also i have switch them around and the one on the bottom wont work and i thinking that the line for that one is some how broken.