That build looks amazing!
Only two things I would change are:
1 ) Windows 7 - I can give you a free copy (yes, it works with a crack, but I've not had anything fail or deactivate on me since BEFORE Windows 7 was formally released: I have it on my PC, laptop, bro's computer, cousin's (SonDoobius) computer, and my other cousin's PC = ZERO issue, and all updates work fine as normal
)
2 ) I would beef up your power supply a little bit. 650W may do the job, but I would bump it up for an extra $__ . I might pick:
http://www.newegg.ca/Product/Product.aspx?Item=N82E16817139022&cm_sp=Cat_Power SuppliesYTCAVideoYT17-139-022 ($139 @ NewEgg Canada)
She's a good one
Only down side is it's not modular (individual cables can be disconnected from the power supply if not in use, so it keeps the case cleaner) - BUT, the HAF X has a shroud that covers the excess cabling of the power supply, so that will be totally in check anyway