To begin with I didn't mean to imply that I thought that my music sounded better in mono; as a matter of fact, I even said I thought something was missing in mono mode.
I like what Hevac says. If music is recorded in mono one should listen to it that way and the converse should also be valid; it makes sense to me. However, I have quite a collection of recordings all of which, as far as I'm aware, are recorded in stereo so that, even though apparently logical, it is an approach that I won't be looking at to resolve my question.
Ultimately, although I appreciate your several responses, I have spent considerable time, effort and money to create the very good stereo setup that I now have so I will simply accept it and abandon the mental calisthenics that led to this post. I still think, btw, that a single speaker for listening to solo guitar makes sense.