idk how familiar you are with Win 8, but in my opinion if its not something you've used before, I'd suggest going with Windows 7 and saving yourself the culture shock. Also, you could probably save a few bucks with the Corsair CX500 model, 500 watts is more than sufficient for that rig.
I'd try to budget in a 250 is gigabyte SSD if you can. Their prices are pretty stable now, and they''re just nice to have.