Not a bad system.
Because It is used I would be asking around $550 that's what I would sell it for in my shop.
PCPartPicker part list: http://pcpartpicker.com/p/2r3Gt
Price breakdown by merchant: http://pcpartpicker.com/p/2r3Gt/by_merchant/
CPU: AMD FX-6300 3.5GHz 6-Core Processor ($116.97 @ OutletPC)
Motherboard: Gigabyte GA-970A-D3 ATX AM3+ Motherboard ($93.98 @ SuperBiiz)
Memory: Corsair XMS3 8GB (2 x 4GB) DDR3-1600 Memory ($93.99 @ Amazon)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($59.98 @ OutletPC)
Video Card: Sapphire Radeon HD 7870 GHz Edition 2GB Video Card ($210.98 @ SuperBiiz)
Case: Rosewill CHALLENGER ATX Mid Tower Case ($49.99 @ Newegg)
Power Supply: Rosewill Green 630W 80+ Certified ATX Power Supply ($59.99 @ Amazon)
Optical Drive: Samsung SH-224BB/RSBS DVD/CD Writer ($23.99 @ Amazon)
Os: Windows 7 Home Prem