Looks like a sweet system, but overkill for what you'll be doing. You won't actualize any benefit from SLI with those games. In fact, I believe that Diablo 3 and Starcraft are more CPU-dependent.
With this in mind, you can scale back to a $150 mobo, a 550w PSU, and 1600 grade RAM. Everything else looks pretty sweet. But with those other things, you'll be spending more money for extra power that you won't use.