I recently bought an emachines EL1360G-UW12P desktop with an AMD E-300 dual-core processor. I'm wondering if I can upgrade the processor and motherboard to something powerful enough for gaming? Will I also have to upgrade the PSU if I do? What mobo cpu combo should I use? I'd prefer an overclockable AMD that I can get fairly cheaply (maybe on eBay or something)! Thanks!