Is powerfull Amps only for low sensitivity speakes?

 I have heard great sounding systems with both very efficient speakers and not so efficient speakers. But I do feel that with dynamic drivers if you go below around 90 DB you cannot get the really really great sound.  No matter how much power you add you cannot get the macro dynamics.   
 I believe the industry moved more towards less efficient speakers because they are much cheaper to manufacture as you don't need the tight tolerances.   And with the transistor it was easier to get big power so efficiency was not quite as important, or so they thought. 

Are powerful amps only for low sensitivity speakers? No.

My 4-way hybrid-horn/dipole system is powered by eight identical Class D amplifiers. Each amp is rated 175W RMS, 325W peak power into 8 Ohms.

The compression driver mid horns and tweeters are very sensitive, about 110 dB/W/meter.

The four 15" woofers in four U-frames are each about 95 dB/W/M.

I don't know the overall system sensitivity - the horns had to be padded down by the active crossover to match the woofers - but it's pretty high. Total power is 1,400 W RMS/ 2,600 W, peak power.

I never push SPLs very high, I want to preserve what's left of my hearing, so usually power is under 1 watt, with brief peaks of 10, or 15 watts, maybe. Lots of head room. Sounds very good.

My 1.5 W/channel Type 45 SET amp, on the other hand, also sounds very good powering sensitive horns. And that little amp has pretty much no headroom.

It's just a hunch but I would be surprised if 60W RMS pumped into 100db sensitivity sepakers doesn't at some point on bass heavy material run toward clipping. This is pretty much what I run and given my fondness of dynamic range and dislike of amp clipping I really wouldn't go below 60W.
For the more technically minded members here, given a 22' by 16.5' with 8'9" ceiling, well trapped room does 60 watts ever clip? I play it pretty loud but do the peaks require the full amp?

Dear Friends, thank you again for your comments.
May I ask your comments also for the difference between single ended triode amps and push pull tube amps in terms of 2nd and 3rd harmonics capabilities.
regards,
ozan