This should be a pretty good build for you :
PCPartPicker part list:
http://pcpartpicker.com/p/1s5Nb
Price breakdown by merchant: http://pcpartpicker.com/p/1s5Nb/by_merchant/
Benchmarks: http://pcpartpicker.com/p/1s5Nb/benchmarks/
CPU: AMD FX-6300 3.5GHz 6-Core Processor ($119.99 @ Newegg)
Motherboard: Asus M5A78L-M/USB3 Micro ATX AM3+ Motherboard ($54.98 @ SuperBiiz)
Memory: Corsair Vengeance 8GB (2 x 4GB) DDR3-1600 Memory ($56.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($69.99 @ Newegg)
Video Card: Gigabyte Radeon HD 7850 2GB Video Card ($165.38 @ Newegg)
Case: Silverstone Redline Series RL04B ATX Mid Tower Case ($32.99 @ NCIX US)
Power Supply: OCZ Fatal1ty 550W 80 PLUS Certified ATX12V / EPS12V Power Supply ($29.50 @ Newegg)
Optical Drive: Lite-On iHAS124-04 DVD/CD Writer ($14.99 @ Newegg)
Total: $526.81
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-08-14 22:47 EDT-0400)