You won't beat this for ~$1250
PCPartPicker part list:
http://pcpartpicker.com/p/3iNNm
Price breakdown by merchant: http://pcpartpicker.com/p/3iNNm/by_merchant/
Benchmarks: http://pcpartpicker.com/p/3iNNm/benchmarks/
CPU: Intel Core i5-4570 3.2GHz Quad-Core Processor ($189.98 @ SuperBiiz)
Motherboard: ASRock B85 Pro4 ATX LGA1150 Motherboard ($69.99 @ Newegg)
Memory: G.Skill Ripjaws Series 8GB (2 x 4GB) DDR3-1600 Memory ($67.50 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($54.99 @ NCIX US)
Video Card: MSI GeForce GTX 780 Ti 3GB Video Card ($659.99 @ Newegg)
Case: Cougar Solution (Black) ATX Mid Tower Case ($39.99 @ Newegg)
Power Supply: Rosewill Capstone 650W 80+ Gold Certified ATX Power Supply ($89.99 @ Amazon)
Operating System: Microsoft Windows 7 Home Premium SP1 (OEM) (64-bit) ($84.98 @ OutletPC)
Total: $1257.41
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-03-29 22:30 EDT-0400)
You could save $189 by dropping down to a regular GTX780