So I have a decent sub on my MET and it does sound good, but I agree that you can pretty much purchase any cheap old subwoofer and it's going to sound pretty good on a pinball machine. My recent STTNG came with a Sony SA-WMSP1. It sounds fantastic on the machine. I have it set on about 1/3 volume, which my wife still complains that it's too loud. I wouldn't want it any louder then that, as I prefer to have nothing over those people that have their subwoofers cranked up way to loud.