heres a cheap gaming pc of $300.
CPU: AMD A8-7600 3.3GHz Quad-Core Processor
Motherboard: ASRock FM2A88M-HD+ Micro ATX FM2+ Motherboard
Memory: G.Skill Ares Series 8GB (2 x 4GB) DDR3-2133 Memory
Storage: 500GB 7200rpm HDD (skip this if your old HDD is still usable)
Power Supply: SeaSonic 300W...