Firstly I would replace the hard drive with a black edition, green edition is a power saver and they are a little slower
you have picked an outdated video card that is generation old, we're on 7xxx series now...soon to be 8xxx series...for $20 more from your 6850 you can pick up 7850 which will give you a nice performance improvement in gaming
for operating system get OEM version as its $100 instead of $170 64 bit version of course
That's a solid build. Very nice ... 3 items to consider:
1. SSD ? I bought one and reused an old HDD for mass storage. I love mine.
2. AMD is releasing the 88xx in the next month or two. This will drive the price down on all previous GPUs.
3. Microcenter CPU & Mobo combos can't be beat. Period. Only catch - gotta go to store to pick them up. If you live by one you could save approx $50.