dB effeciency vs speaker configuration

I tend to like low powered amps, tube or solid state class A.... with higher efficiency speakers.    I've had some great sounding lower efficiency speakers, 83 to 86 dB/w  but they all ran out of steam quickly and needed a lot of power to shine.    My current setup is a pair of Klipsch Heresy III with a pair of 40 w Quicksilver monos and they sound as close to live music as I've ever had at home.

" sound as close to live music as I’ve ever had at home ".......this, is what it is all about !..........I have heard so many multi 6 figure systems, that do not do this, using live, unamplified music, as my reference........

What impedance and what sensitivity sounds the best?
From an amplifier point of view, the less distortion the amp has to make to do its job the better. To this end, higher impedance followed by higher efficiency will result in smoother more detailed sound, all other things being equal.

The reason this is so is that quite simply all amps have less distortion driving higher impedances. Amps also tend to make less distortion when not having to make a lot of power within their power envelop.

There are some excellent 4 ohm speakers out there! But the simple fact is that if they were 8 ohms or even 16 while otherwise being the same design, they would sound smoother and more detailed with greater impact simply because the amplifier would be making less distortion. Put another way, just because an amplifier can drive a difficult load is not the same as saying its also sounding its best while doing so!

 Best answer is not answer to you question , One speakers with 85db can sound better them speaker 95 db,   Another brand with 95 db will overperform speaker 85db  , same thing with impedance and box enclosure design.    

Not to hijack the thread, but what determines speaker efficiency? Is it the materials used, or is it something else?