jcd; it's been my experience that it is not the amp that is the limiting factor in making music sound good at low volume, but rather it's the speakers. And I don't think speaker sensitivity has much to do with it either.
For example, My Vandersteen 3As or 3Asigs both sounded very good at low volumes and I enjoyed that, but I recently (5 months ago) acquired Vand. 5s, and the 5s have to be driven at distinctly louder volume to sound good. The 3As and 5s have about the same sensitivity. I have read where reviewers have noted this phenomenon too. I think it has to do with the design of the speaker. As the 5s continue to breakin, they are now sounding better at lower volumes, but still must be played louder to sound good. Good Luck. Craig.
For example, My Vandersteen 3As or 3Asigs both sounded very good at low volumes and I enjoyed that, but I recently (5 months ago) acquired Vand. 5s, and the 5s have to be driven at distinctly louder volume to sound good. The 3As and 5s have about the same sensitivity. I have read where reviewers have noted this phenomenon too. I think it has to do with the design of the speaker. As the 5s continue to breakin, they are now sounding better at lower volumes, but still must be played louder to sound good. Good Luck. Craig.