The cheapest P67 board that still lets you overclock, and either see how everything pans out, or keep it and fit Ivybridge etc and get 16X PCI-E lanes at spec 3.0 - http://www.overclockers.co.uk/showproduct.php?prodid=MB-448-AS&groupid=701&catid=5&subcat=1906
And just run a single card setup.
And just run a single card setup.