See
http://www.tomshardware.com/forum/261222-31-build-advice
Try -
CPU: AMD FX-6300 3.5GHz 6-Core Processor ($94.99 @ NCIX US)
Motherboard: Gigabyte GA-970A-D3P ATX AM3+/AM3 Motherboard ($72.89 @ OutletPC)
Memory: G.Skill Ares Series 8GB (2 x 4GB) DDR3-1600 Memory ($48.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($46.89 @ OutletPC)
Video Card: Gigabyte Radeon R9 270X 2GB WINDFORCE Video Card ($152.98 @ Newegg)
Case: Corsair 200R ATX Mid Tower Case ($59.99 @ Micro Center)
Power Supply: XFX TS 550W 80+ Gold Certified ATX Power Supply ($73.99 @ NCIX US)
Operating System: Microsoft Windows 8 OEM (64-bit) ($92.95 @ OutletPC)
Total: $643.67