That motherboard isn't going to run SLI. And it would suck for X-fire as the 2nd slot is only x4. All I have is anecdotal evidence but from my experience with the ASRock board I setup in my dads machine it wouldn't run SLI with an x16/x4 slot setup. I even hacked it and it was a no go. I believe it's because the x4 slot is ran from the chipset and not through the CPU like the x16 slot is and the Nvidia drivers don't recognize it properly. However it will run X-fire in a reduced capacity. Also after about a year now the ASRock board is losing it's ability to overclock like it did when new.