Don Firth wrote:
"[...] I've heard Segovia, Christopher Parkening, Pepe Romero, and others play in fairly sizeable theaters with no amplification whatsoever, and their guitars could be heard loud and clear everywhere in the theater."

I think it probably has a lot to do with the rooms. In a theater or auditorium with good acoustics, it's remarkable how what is spoken, sung or played on stage can be heard in the furthest corners. A lot of places now have more-or-less discrete amplification, too.

Don Firth wrote:
"I've never had any problems that way with my classics, even when I've used one of my "second" guitars. And I just use my fingernails. If you're not getting much volume, you might want to check your right hand position. And use rest-strokes whenever you can."

I didn't quite follow the discussion about whether it should be "classic" or "classical". I prefer the term "classical", with no wish to offend anyone. The word "classic" has become so overused, from "classic Coke" to "classic rock", etc., ad nauseum, that I try to avoid it. I will still say "classic cars", though.

I don't have any trouble with my volume, but then I only play for myself. With amplification, it wouldn't be a problem. My guitar isn't that great, and I've wanted a better one for a long time, but it doesn't seem to be quieter than average. Thank you for the suggestions, anyway.