PCPartPicker part list:
http://pcpartpicker.com/p/1Wmst
Price breakdown by merchant: http://pcpartpicker.com/p/1Wmst/by_merchant/
Benchmarks: http://pcpartpicker.com/p/1Wmst/benchmarks/
CPU: Intel Core i5-3350P 3.1GHz Quad-Core Processor ($177.98 @ SuperBiiz)
Motherboard: MSI B75MA-P45 Micro ATX LGA1155 Motherboard ($70.80 @ Amazon)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600 Memory ($63.75 @ Newegg)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($59.98 @ OutletPC)
Video Card: MSI Radeon R9 270X 2GB Video Card ($197.98 @ SuperBiiz)
Case: Corsair 200R ATX Mid Tower Case ($49.99 @ NCIX US)
Power Supply: Corsair Builder 500W 80 PLUS Bronze Certified ATX12V Power Supply ($24.99 @ Newegg)
Total: $645.47
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-11-02 13:13 EDT-0400)