PCPartPicker part list:
http://pcpartpicker.com/p/ooaz
Price breakdown by merchant: http://pcpartpicker.com/p/ooaz/by_merchant/
Benchmarks: http://pcpartpicker.com/p/ooaz/benchmarks/
CPU: Intel Core i5-3470 3.2GHz Quad-Core Processor ($149.99 @ Microcenter)
Motherboard: ASRock H77M-ITX Mini ITX LGA1155 Motherboard ($94.99 @ Microcenter)
Memory: Patriot Viper 3 8GB (2 x 4GB) DDR3-1600 Memory ($24.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($49.99 @ Newegg)
Video Card: Galaxy GeForce GTX 660 2GB Video Card ($219.99 @ Newegg)
Case: Cooler Master Elite 120 Advanced (Black) Mini ITX Tower Case ($39.99 @ Newegg)
Power Supply: XFX ProSeries 450W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply ($42.99 @ NCIX US)
Optical Drive: Lite-On iHAS124-04 DVD/CD Writer ($17.99 @ SuperBiiz)
Total: $640.92
(Prices include shipping, taxes, and discounts when available.)