What do you think of my gaming PC build?

Solution
Then I would suggest these changes. A 7950, a better PSU, and a CPU cooler so you can overclock.

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: AMD FX-6300 3.5GHz 6-Core Processor ($117.99 @ SuperBiiz)
CPU Cooler: Cooler Master Hyper 212 Plus 76.8 CFM Sleeve Bearing CPU Cooler ($19.99 @ Newegg)
Motherboard: Asus M5A97 R2.0 ATX AM3+ Motherboard ($80.99 @ Newegg)
Memory: Corsair Vengeance LP 8GB (2 x 4GB) DDR3-1866 Memory ($49.99 @ Newegg)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($58.98 @ Outlet PC)
Video Card: HIS Radeon HD 7950 3GB Video Card ($189.99 @...
Then I would suggest these changes. A 7950, a better PSU, and a CPU cooler so you can overclock.

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: AMD FX-6300 3.5GHz 6-Core Processor ($117.99 @ SuperBiiz)
CPU Cooler: Cooler Master Hyper 212 Plus 76.8 CFM Sleeve Bearing CPU Cooler ($19.99 @ Newegg)
Motherboard: Asus M5A97 R2.0 ATX AM3+ Motherboard ($80.99 @ Newegg)
Memory: Corsair Vengeance LP 8GB (2 x 4GB) DDR3-1866 Memory ($49.99 @ Newegg)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($58.98 @ Outlet PC)
Video Card: HIS Radeon HD 7950 3GB Video Card ($189.99 @ Newegg)
Wireless Network Adapter: Asus PCE-N15 802.11b/g/n PCI-Express x1 Wi-Fi Adapter ($29.36 @ SuperBiiz)
Case: Cooler Master HAF 912 ATX Mid Tower Case ($49.99 @ Newegg)
Power Supply: Antec High Current Gamer 620W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply ($54.99 @ NCIX US)
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer ($16.98 @ Outlet PC)
Operating System: Microsoft Windows 8 (OEM) (64-bit) ($95.87 @ Outlet PC)
Monitor: Asus VS238H-P 23.0" Monitor ($129.99 @ NCIX US)
Total: $895.11
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-09-22 18:36 EDT-0400)
 
Solution
Makes the CPU run faster. In cases where actual performance - like the FPS in a game - is limited by the CPU, it can improve performance significantly. In cases where the CPU isn't the limiting factor, it won't do much. But you basically get a faster CPU without paying extra (except for the price of a better cooler that is required to deal with the extra heat).