OS: I think you don't need Pro. Windows 7 Home Premium is better for your purpose, IMO.
RAM: Go to Asus website and read their RAM compatibility list. I don't remember it off the top of my head. In my current build, I originally went with Corsair but after checking that it's not on the compatibility list, I switched to OCZ which was the correct decision. I found a couple of forum posts through Google searches that say the Corsair RAM which I intended to buy was unstable with the Asus board.
PSU: I don't know much about Ultra PSU's but 750W is probably enough for your needs.
Case: The HAF 932 is a great case but will attract a lot of dust. And I think the Silverstone FT02 is a lot more silent.