Final product list on my first build, any thoughts?

Processor: Intel Core i5 3570k $189.99 Micro Center

Motherboard: ASRock Z77 Extreme 4 $89.99 (combo deal with i5 3570k) Micro Center

CPU Cooler: Thermal Take Frio 47.99 Amazon

PSU: Corsair Enthusiast Series 850 Watt 80 Plus $127.99 Amazon

Case: Sentey Extreme Division Arvina GS-6400 $49.99 Micro Center

Optical Drive: Samsung SH-B123L/RSBP Internal DVD-Writer (BD/DVD/CD) $64.99 Amazon

Ram: Corsair Vengeance Blue 16 GB DDR3 SDRAM Dual Channel Memory Kit $95.99 Amazon

Still trying to figure out what to do with my GPU, I have a PNY GTX 550ti, and can get another one and SLI for $89.99 (Best Buy /w $40 in RZ credit)

I have a 640Gb WD Caviar Black I am going to use, and upgrade to an SSD later.

Also I already have an unused license of Windows 7 Pro I bought for $64.95

Total $821.91 - $367 Amazon credit from trading in textbooks

= $454.91 out of pocket cash

Anything you would change? Is the PSU Overkill?