I am considering the RIIIE and the MSI Big Bang X Power. I like the expansion slot layout on the MSI board better.
Dont go with the MSI board, its not as good and some people report instability problems.
Have you looked at the Gigabyte G1 Sniper.
Best boards are the RIIIE, RIIIE BE, Gigabyte X58 OC, and the Gigabyte G1 killer.