Couldn't find any Corsair AX in the 500W range, they seem to start at 760W.
Whole kit without OS might sell for $600 used.
PCPartPicker part list:
http://pcpartpicker.com/p/3TVDkL
Price breakdown by merchant: http://pcpartpicker.com/p/3TVDkL/by_merchant/
CPU: AMD Phenom II X4 945 3.0GHz Quad-Core Processor ($80.98 @ SuperBiiz)
Motherboard: Asus M5A97 R2.0 ATX AM3+ Motherboard ($87.99 @ Amazon)
Memory: Corsair Vengeance 16GB (4 x 4GB) DDR3-1600 Memory ($169.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($52.92 @ Amazon)
Video Card: EVGA GeForce GTX 760 2GB Superclocked ACX Video Card ($209.99 @ NCIX US)
Case: Cooler Master Elite 430 ATX Mid Tower Case ($27.99 @ Newegg)
Power Supply: Corsair CX 500W 80+ Bronze Certified Semi-Modular ATX Power Supply ($59.99 @ Amazon)
Monitor: Asus VE228H 21.5" Monitor ($129.99 @ Amazon)
Total: $819.84
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-06-12 18:36 EDT-0400