I agree with the better power supply.
I believe that would be a great system.
I am going to suggest one very similar to yours to a buddy who wants to build a pc bad, after he came over and played Rainbow Six Vegas.
Enjoy your build,and if you have any trouble the great people here will help you out.
Cooler Master CM Stacker Case
Asus P8Z68 V Pro/Gen 3
Cooler Master V6 GT Heat Sink
8 GB G-Skill DDR 3 1600
GTX 570 SLI
Asus Xonar Essence STX Sound Card
Grado RS1i & AKG Q701 Headphones
MAD EAR + HD Headphone Amp
Corsair CMPSU 850 Watt
Western Digital Black 500 GB
Crucial M4 64 GB SSD For Windows 7 64 Bit
Samsung 2494SW 24" LCD
Logitech G5 Mouse
Logitech G110 Keyboard