Not specific to your CPU question, but just an FYI. As the Mame devs more accurately emulate the hardware (discrete sound seems to be a big one) the CPU power to actually emulate the hardware keeps increasing. So, if you use an older version of Mame you will, probably, get more speed and thus need a less powerful CPU. But, if you plan on using the latest version, then a the same CPU that works for older version may not be able to run things at full speed on the latest build. Just food for thought.