I also meant to comment about the Baltimore Consort and Custer LaRue. We had them as a part of our performance series back about six years ago. They performed, sans amps, in a 1000 seat auditorium, put on a great performance and were heard nicely. The diffence, however, between them and a dance is that people know they're supposed to shut up and listen at a concert. Even solo classical guitarists can be heard in a decent concert hall.

I can't image the Baltimore Consort, or a classical guitarist, being heard at a dance in a gym or barn or church meeting hall - it's two different entirely different beasts!
To my mind the traditional instruments that can generally be heard, unamped, are bagpipes, accordions, and fiddles.