I have an HP iPAQ 4350 that does fine with PocketNester. It's about a year and a half old, but still nice (400mhz, 64mb Ram). I don't see any reason that a PPC with even half that couldn't run an NES emulator. Almost anything you buy new should be able to handle it, but I agree that you should get the best you can afford, as there are a lot of non-retro games that will demand more speed and memory, and are really very entertaining.