^ Don't bother with the 950.
Overall, excellent build. You can't do much better than that.
I would like to have dual video cards if possible (only if it is better then one). Therefor the reason for a 850W power supply because planning on upgrading later. Although I would like to have duals from the start.
No point. The GTX470 can handle most games fine @ 1920*1080. By the time you'll need more horsepower (ie Crysis 2,etc) you'll be able to add a 2nd GTX470 for significantly cheaper, esp. with the ATI 6xxx cards coming out soon.