Nearly best available performance without going to extreme in any one direction. No overclocking.
If you want more graphics horsepower, you can swap in a GTX770 or R280X (never mind, keep forgetting about the bit mining price wars going on with ATI cards), but would have to sacrifice some CPU performance and probably go AMD.
PCPartPicker part list:
http://pcpartpicker.com/p/31jOE
Price breakdown by merchant: http://pcpartpicker.com/p/31jOE/by_merchant/
Benchmarks: http://pcpartpicker.com/p/31jOE/benchmarks/
CPU: Intel Core i5-4570 3.2GHz Quad-Core Processor ($197.98 @ SuperBiiz)
Motherboard: ASRock H87 Pro4 ATX LGA1150 Motherboard ($93.98 @ SuperBiiz)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1866 Memory ($76.50 @ Newegg)
Video Card: Asus GeForce GTX 760 2GB Video Card ($239.99 @ Newegg)
Power Supply: XFX 550W 80+ Bronze Certified ATX Power Supply ($59.99 @ Newegg)
Total: $659.49
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-02-27 20:32 EST-0500)