Of course... 500 mhz hardly runs mame anymore. They keep upping the specs, so even older games do not run very fast.
Im still running an amd900... and its barely passable on some games. I fired up a PIII 550 the other day, and just loading the darn mame32 games list verify when it first runs, was taking too long for me.
Im sure the technology will get better. I think Id wait to make a handheld for a bit. But a bartop sounds like a nice portable project to me.