This is a touchy area, a lot of guitarists are picky about the way a speaker should sound. Some of them I know took out there original Eminence speakers from there Fender amps, and replaced them with EV12L's or JBL E120's thinking they would sound better. They were wrong, they claimed they were to "clean" sounding and just couldn't get the tone they're looking for out of them. So they went back to the originals, but that's electric, which is a different story. Guitarists tell me it's a combination of all 3, the amp/head your using, the type of speaker, and what type of enclosure it's in, play an important role in the tone. But thats electric.So using something like a EV 12L or a JBL E120 for an acoustical or "natural sounding" insturment should work out pretty good since there to "clean sounding" of a speaker as electric guitarists have said.
Just look at how many different speakers Eminence makes just for there guitar line alone.