i was originally going to post a quadro but the only one in your price range only has 64 cuda cores and that is what you need most
PCPartPicker part list:
http://pcpartpicker.com/p/3bQ5n
Price breakdown by merchant: http://pcpartpicker.com/p/3bQ5n/by_merchant/
Benchmarks: http://pcpartpicker.com/p/3bQ5n/benchmarks/
CPU: AMD FX-8320 3.5GHz 8-Core Processor ($159.99 @ Newegg)
Motherboard: ASRock 990FX Extreme3 ATX AM3+/AM3 Motherboard ($109.99 @ Newegg)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600 Memory ($69.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($54.98 @ OutletPC)
Video Card: Asus GeForce GTX 650 Ti 1GB Video Card ($129.99 @ NCIX US)
Case: Xigmatek Recon ATX Mid Tower Case ($29.99 @ Newegg)
Power Supply: XFX 550W 80+ Bronze Certified ATX Power Supply ($49.99 @ NCIX US)
Optical Drive: LG GH24NSB0 DVD/CD Writer ($14.99 @ Newegg)
Operating System: Microsoft Windows 7 Home Premium SP1 (OEM) (64-bit) ($89.98 @ OutletPC)
Total: $689.89
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-03-17 23:22 EDT-0400)
the 750 ti only has 640 cuda cores the 650 ti has 768 cuda's so you should see better performance out of it.