looks like you want the 975x chipset. No SLI MB can run Xfire, and I do not see any Nvidia chipsets that support Xfire.
You definitely do not want a P965 chipset either. The 2 PCI-E slots are not balanced. Primary runs 16 lanes to the northbridge, but secondary only 4. Get a P975 Intel or an ATI/AMD chipset board to run Crossfire.