Instead get 2 500GB hard drives and set up Raid-0 for great performance. You'll get a much better framerate that way.
And it appears so you'll be able to max out just about everything for the next couple of years.
The parts look good but I don't know about 520 watts and a 6870...
That's what I was thinking. Get at least a 700w one, so in the future you can have enough power to possibly crossfire that card. :o
Newegg's PSU calculator comes up as 490W PSU is needed.
It says itself, it's only a reference. If it is correct, that's only 30w left. You need much more than that or you'll burn it out.
I would do at least 100 more than what it says, always. Get a 700w one.