CPU: AMD A8-5600K 3.6GHz Quad-Core Processor ($92.23 @ Amazon)
Motherboard: MSI FM2-A75MA-E35 Micro ATX FM2 Motherboard ($56.00 @ Amazon)
Memory: G.Skill Ripjaws Series 4GB (1 x 4GB) DDR3-1600 Memory ($35.99 @ Newegg)
Storage: Toshiba 1TB 3.5" 7200RPM Internal Hard Drive ($59.99)
Case: Thermaltake VL80001W2Z ATX Mid Tower Case ($21.99 @ Microcenter)
Power Supply: Corsair Builder 430W 80 PLUS Bronze Certified ATX12V Power Supply ($39.99 @ Microcenter)
Total: $306.19
This si nice build for 300$ if you already have case.