I agree with the switch to an Intel board. The 2500k is king of value, and it definitely kicks some serious performance out. BD is a nice thought experiment, but the performance does not justify pricing.
The 580 is a conundrum. While an excellent card, the 7970 is out right now. An extra hundred gets you significantly better performance for 99% of the games out there (not using GPU Physx), and a lower power draw. For what will likely be a very similar price, the 7950 is coming out soon. If $500 is price max, then keep it. If you are flexible then run with something at the top of the AMD stack.
Otherwise, a very capable gaming build.