The single most common mame audio setup is a set of PC speakers taken apart and placed in the cabinet, or the small amp out of a cheapo PC speaker powering a pair of 5" speakers.
That is pretty much 100 percent arcade authentic for most games. Most games had one CHEAP speaker in them.
I usually do the cheapo PC speaker route, which is more than enough, heck, I usually only have the volume at like 10 percent.