I'd just like to add in here:

If you're going to be running multiple cards (which I assume you are), you're going to want to get a motherboard with a chipset that has enough bandwidth to support all of them fully. If you have two PCIe slots running at x8, and the rest running at x1, then that's really no good. I suggest sticking with the x38, x48, x58 intel chipsets for this reason. Something that can hold x16 on both lanes, and more.