I remember being shocked at how good my old Tannoy System 10 DMT Mk1 sounded at low volume, compared to my previous speakers. I could turn them right down and vocals still had life, and projected into the room, with good bass too. Crank them up to almost nightclub levels, and they still sounded great.
The Tannoys didn't sound good with electric guitars though (soft), which I put down to the self damping of the plastic drivers. Controversial, I know, but had the same thing happen with a number of previous plastic coned drivers, so can only think that's what it was.
I was using highly modified Naim 62 / 250 at the time, and I'm sure that played a part, because certain power supply mods really increased dynamics.