The Asus Maximus II Formula would be my choice. Mainly due to the board reliability and DDR2 ram prices. Since there is alot of Compatibility/Stability problems with the nvidia cipset 780i motherboards (mainly BSODS and ram).
Depending on how much you are willing to spend on this Build. But you could also go with a Core i7/X58 build, which will allow you to do either SLI or Crossfire.