I'd drop the 4300 and get a 6300 as its only $15 more and its a better gaming CPU. I would drop the 16Gb of ram down to 8Gb(2x4Gb) and use the money saved there to get a GTX 760(faster gamer than a 7870).
PCPartPicker part list:
http://pcpartpicker.com/p/2nD6E
Price breakdown by merchant: http://pcpartpicker.com/p/2nD6E/by_merchant/
Benchmarks: http://pcpartpicker.com/p/2nD6E/benchmarks/
CPU: AMD FX-6300 3.5GHz 6-Core Processor ($109.99 @ Amazon)
Memory: G.Skill Sniper Series 8GB (2 x 4GB) DDR3-1866 Memory ($68.00 @ Newegg)
Video Card: EVGA GeForce GTX 760 2GB Video Card ($244.98 @ SuperBiiz)
Total: $422.97
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-12-21 01:37 EST-0500)