Les: I reckon that I have performed in every conceivable venue in the 35 years that I have been pickin' bluegrass and Appalachian music. We always told ourselves that folks were paying to have us perform, and if they chose not to listen, it was their loss--but that really didn't help our frustration much.

I don't know how many folks you have in your group, or what the difference in the voice timbre of the instruments might be, and all of that makes a difference. If you're interested primarily in having your vocalist(s) heard, we found that a speaker/amp intended to be used with an electronic keyboard is quite suitable, with regard both to fidelity and portability. Ours has connections for two microphones, and volume sufficient for us to override bar gigs when we need to. I admire your standards of purity for performing acoustic music, but you must remember that the average bar gig is not really a suitable setting for the acoustic music.