Hmm... Those Builds were great, and Here's my Recommendation assuming that you already have a legal copy of Windows and also reducing the HDD size to 500Gb :
PCPartPicker part list:
http://pcpartpicker.com/p/328QK
Price breakdown by merchant: http://pcpartpicker.com/p/328QK/by_merchant/
Benchmarks: http://pcpartpicker.com/p/328QK/benchmarks/
CPU: AMD FX-8320 3.5GHz 8-Core Processor ($149.99 @ TigerDirect)
Motherboard: Gigabyte GA-78LMT-S2 Micro ATX AM3+ Motherboard ($42.99 @ Amazon)
Memory: Patriot Signature 8GB (1 x 8GB) DDR3-1600 Memory ($67.98 @ Newegg)
Storage: Crucial V4 32GB 2.5" Solid State Disk ($42.95 @ Amazon)
Storage: Western Digital AV-GP 500GB 3.5" 5400RPM Internal Hard Drive ($45.94 @ Amazon)
Video Card: Sapphire Radeon HD 7870 GHz Edition 2GB Video Card ($192.55 @ Newegg)
Case: NZXT Source 210 (Black) ATX Mid Tower Case ($29.99 @ Microcenter)
Power Supply: Corsair Builder 430W 80+ Bronze Certified ATX Power Supply ($19.99 @ Newegg)
Optical Drive: LG GH24NSB0 DVD/CD Writer ($15.99 @ TigerDirect)
Total: $608.37
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-03-01 09:38 EST-0500)
Well, If you could increase the budget Slight more, you could get the More powerful R9 270X. I know that R'HD 7870 is becoming Previous Gen. Card but still it produces more Power than the R9 270.
The CPU is also more Powerful if you want some Computing Power assuming you haven't described your works you would do. Also, An SSD would Increase overall system Speed on that system. You could use that as a Cache SSD.
That CX430 would be able to Handle that whole system if you are not into Over clocking.