In my cabinet I'm running an AMD APU A10-5800K (4 x 4.2GHz CPUs - plus Radeon 7660D GPU), 4GB RAM. It was cheap at the time and sounded good when I thought all I'd be doing was MAME through Hyperspin, but I have since branched out and realized I need more. I've heard that processing power is the most important part. Upgrading to 16GB RAM probably won't fix the issue, right? I also obviously need a real graphics card.