I think you would be quite pleased with this build here. It is an increase of only $130 and gets you quite a bit more performance.
PCPartPicker part list:
http://pcpartpicker.com/p/nfQLwP
Price breakdown by merchant: http://pcpartpicker.com/p/nfQLwP/by_merchant/
CPU: AMD FX-6300 3.5GHz 6-Core Processor ($109.99 @ Amazon)
Motherboard: MSI 970A-G46 ATX AM3+ Motherboard ($78.98 @ OutletPC)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-2133 Memory ($71.10 @ Newegg)
Storage: Kingston SSDNow V300 Series 120GB 2.5" Solid State Drive ($64.99 @ Micro Center)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($54.98 @ OutletPC)
Video Card: MSI GeForce GTX 750 Ti 2GB TWIN FROZR Video Card ($129.99 @ Newegg)
Case: Apevia X-DREAMER4-BL ATX Mid Tower Case ($59.99 @ Mwave)
Power Supply: Corsair CX 600W 80+ Bronze Certified Semi-Modular ATX Power Supply ($44.99 @ Newegg)
Optical Drive: LG GH24NSB0 DVD/CD Writer ($14.99 @ Newegg)
Total: $630.00
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-06-16 12:44 EDT-0400
Also, this build is without an operating system. So if you also need a new OS, tack on another $80.