Here's an overally very solid build for under $750 :
PCPartPicker part list:
http://pcpartpicker.com/p/3gqU4
Price breakdown by merchant: http://pcpartpicker.com/p/3gqU4/by_merchant/
Benchmarks: http://pcpartpicker.com/p/3gqU4/benchmarks/
CPU: AMD FX-6300 3.5GHz 6-Core Processor ($109.99 @ Amazon)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($29.99 @ NCIX US)
Motherboard: Asus M5A99X EVO R2.0 ATX AM3+ Motherboard ($109.99 @ NCIX US)
Memory: G.Skill Ares Series 8GB (2 x 4GB) DDR3-1600 Memory ($79.98 @ OutletPC)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($57.98 @ OutletPC)
Video Card: MSI GeForce GTX 760 2GB Video Card ($239.99 @ Newegg)
Case: Corsair 200R ATX Mid Tower Case ($39.99 @ Newegg)
Power Supply: Antec High Current Gamer 620W 80+ Bronze Certified Semi-Modular ATX Power Supply ($59.99 @ NCIX US)
Optical Drive: Samsung SH-224DB/BEBE DVD/CD Writer ($15.98 @ OutletPC)
Total: $743.88
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-03-25 19:22 EDT-0400)