Take a look at Bose's own ads... solo guitarists setting up to play coffee house style. Why would HE need stereo..? Take a look at how Bose envision a band using them. One EACH (guess they all are doctors in their spare time!)...

Then listen to those that actually DO use them as a stereo system. To be honest, sounds like IAN is the only one answering your question (from experience, anyway). Everyone else (including those with mono systems) is speculating.

Diki-ering, if you like!