PCPartPicker part list:
http://pcpartpicker.com/p/1EcI1
Price breakdown by merchant: http://pcpartpicker.com/p/1EcI1/by_merchant/
Benchmarks: http://pcpartpicker.com/p/1EcI1/benchmarks/
CPU: AMD A10-6800K 4.1GHz Quad-Core Processor ($134.99 @ Amazon)
Motherboard: MSI FM2-A55M-E33 Micro ATX FM2 Motherboard ($44.98 @ Outlet PC)
Memory: Kingston Predator Series 8GB (2 x 4GB) DDR3-2133 Memory ($58.61 @ NCIX US)
Case: Rosewill FB-03 ATX Mid Tower Case ($19.99 @ Newegg)
Power Supply: Antec Basiq 430W 80 PLUS Certified ATX12V Power Supply ($43.44 @ Outlet PC)
Total: $302.01
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-09-15 19:37 EDT-0400)
use your hdd from your old system
this is as good as it gets for 300