malbluff

Honorable
A slightly different approach, which would give slightly better performance (Your build doesn't seem to have a power supply. Is there a reason.)
PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: Intel Core i5-3450 3.1GHz Quad-Core Processor ($186.97 @ CompUSA)
Motherboard: ASRock H77M Micro ATX LGA1155 Motherboard ($69.99 @ Newegg)
Memory: Corsair Vengeance 8GB (2 x 4GB) DDR3-1600 Memory ($39.99 @ Newegg)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($74.99 @ SuperBiiz)
Storage: Crucial M4 64GB 2.5" Solid State Disk ($72.16 @ Adorama)
Video Card: Gigabyte Radeon HD 7850 2GB Video Card ($196.97 @ Newegg)
Case: Antec Three Hundred Two ATX Mid Tower Case ($54.98 @ NCIX US)
Power Supply: XFX ProSeries 450W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply ($44.99 @ NCIX US)
Optical Drive: LG GH24NS90 DVD/CD Writer ($15.99 @ Newegg)
Operating System: Microsoft Windows 7 Home Premium SP1 (64-bit) ($91.99 @ Amazon)
Total: $849.02
(Prices include shipping, taxes, and discounts when available.)
 

malbluff

Honorable
One note on my build. You could, if you wish, drop the SSD, and use single higher performance HDD. Which would free up some funds to use an overclockable i5-3570K (and suitable mobo), either making use of a combo deal, from Newegg, or if you have one nearby, Microcentre.
 
Check out my $650 build here:
http://www.squidoo.com/electronicandmore
Swap the 7850 for the 7870 (+$65 (before $20 MIR))
http://www.newegg.com/Product/Product.aspx?Item=N82E16814131466&name=Desktop-Graphics-Cards
OS (+$92): http://www.amazon.com/Windows-Premium-64bit-System-Builder/dp/B004Q0PT3I%3FSubscriptionId%3D19BAZMZQFZJ6G2QYGCG2%26tag%3Dsquid1240995-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D165953%26creativeASIN%3DB004Q0PT3I
Total: $797

You get a MUCH better GPU, B75 can overclock just no voltage tweaking but you'll have to get the i5 3570K if you want to do so, and a better PSU. It will be up to you if you want to get an SSD.