To answer the question aimed directly to the M50: Yes; the M50s sound great at lower volumes.

The M50s are, of course, the more laid-back of the Axioms, but if that is the presentation someone is looking for, they are a fabulous speaker. For most TV viewing they quietly go about their business unless the programming asks them to sing out loud, and then they certainly do!! But they are just as accurate while playing softly as they are when called upon to have some real fun!
Rich.