Ok. In case you need OS:
PCPartPicker part list:
http://pcpartpicker.com/p/qrg2WZ
Price breakdown by merchant: http://pcpartpicker.com/p/qrg2WZ/by_merchant/
CPU: AMD FX-6300 3.5GHz 6-Core Processor ($109.98 @ OutletPC)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($24.99 @ Newegg)
Motherboard: Gigabyte GA-970A-UD3P ATX AM3+ Motherboard ($73.99 @ Newegg)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1866 Memory ($79.99 @ NCIX US)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($52.91 @ OutletPC)
Video Card: MSI Radeon R9 270 2GB TWIN FROZR Video Card ($139.99 @ Newegg)
Case: Cougar Solution (Black) ATX Mid Tower Case ($37.99 @ Mwave)
Power Supply: Corsair Builder 600W 80+ Bronze Certified ATX Power Supply ($39.99 @ Newegg)
Optical Drive: Asus DRW-24F1ST DVD/CD Writer ($14.99 @ Newegg)
Operating System: Microsoft Windows 8.1 (OEM) (64-bit) ($89.98 @ OutletPC)
Total: $664.80
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-08-01 22:18 EDT-0400
You can drop the cooler and it will bring you to $640, but you'll lose OCing capability ( the cooler is something you can always pick up later however, and you only need it if you're OCing ). Thai build will play most games on high. If you don't need an OS you can get a r9 280 which plays most games on ultra