I just got Zu Definitions. They're 101 db efficient at 6 ohms and fear no volume, or lack thereof.
Part of my demo to others is to play a known song, and about halfway through to turn the volume down. And down, and down, and down. They literally need to be *almost* off before the full range is lost. I haven't had the speakers long, but the 4 people I've demo'd them to have all been most impressed with this element of their performance.
I credit this to the lack of any crossover elements at all from 40 hz to 12 khz - no electronics to get fussy with signal transfer. And, no inefficient drivers of different properties trying to get along.
These also have 4 powered 10" sub drivers in back. There's no crossover setting, but gain is easily adjustable via rear-mounted volume control.
They are very detailed, but not in the typical way. Nuanced would be more appropriate.
Call Sean at Zu. If there's someone in your area who's got them, he'll probably put you in touch.
Good luck!