I am planning a build, and like the bitfenix prodigy-M case. I have a 3770K, 1155 socket. I am toying with the idea of installing a single Radeon 8950, and when needed, installing the other in Xfire mode. I am confused about which motherboards can accomodate two double-wide cards without covering over a slot....how do I see this in the motheboard specs?