Three words: Low level detail. Sometimes the problem lies in the passive parts of your louspeakers (binding posts, wiring, crossovers, etc). sometimes it's the drivers themselves. Sometimes the problem is farther up the signal chain. And yes, high-efficiency/high-sensitivity speakers, especially single driver speakers, and well executed multidriver speakers are usually good in this regard. It also helps to have speakers that sound coherent (as cut from the same sonic cloth) over as much of the volume range as possible.
I don't have all of the answers. I've only been at this for less than 4 years.
I don't have all of the answers. I've only been at this for less than 4 years.