Emulating the arcade experience will not fill the garage with sound, they are positioned so that the person at the machine will hear it well and not a lot gets to the rest of the area its in, otherwise arcades would be unbearably loud as opposed to the annoyingly loud that they are

If your going for authentic arcade and are not going to be using it as a jukebox then a couple of 4" coaxial car speakers hooked to that amp I mentioned in the shielded speakers thread will be all you need.
If you are doing a jukebox then that will be woefully in-adequate and you may as well use a $20 boombox from kmart to play your tunes on. A jukebox is basically a fancy name for a kick ass stereo thats not in a car
