Speaker and amp pairing

There are lots of variables in play, but I learned a long time ago that not all watts are created equal, and that the measured specs for many amplifiers don't tell the whole story about how well they'll actually drive a speaker.  Nor the do specs indicate how an amp will sound.  Some of that is due to the fact that speaker impedances vary a lot, but most don't pose an unusually difficult load for a decent amp. 

If the nominal speaker impedance is rated at 8 ohms, most speakers will do fine with a well designed amp that has good current flow, unless the speaker is known to have a very low or complex impedance.  If nominal impedance is 4 ohms, you'll want an amp that control a low impedance speaker well.  It shouldn't be too difficult to research if any speakers you're interested in are known to to pose very low and/or difficult to drive loads, or how well a particular amp handles more difficult loads.  

As long as a few minimum impedance requirements are considered, I've always tended to focus more on how the speakers and amp sound together, with more focus on the speakers first, then try to find an amp that's capable and that I like the sound of.  It can take time, and trial and error, but can always bring a lifetime of enjoyment when done well.  

I just switched from a 50 watt a/b amp for a 150 watt Class D amp at 8 ohms. My speakers are 4 ohms and this amp will provide 250 watts.
my room is  small 12x14’ and not at loud levels. The higher power amp provides lots of clean power - bass so clean and accurate and zero heat!
not my first class D amp-

you have to listen ! And with the absence of audio salons , a good choice is impossible via mail order! I sent back the 50 watt/ ch amp and it’s a PIA  and only by luck did the next amp sync!

millercarbon and knotscott make the most sense here. Impedance, watts, sensitivity, etc., all come into play. Looking at those numbers and pairing with an amp certainly come into play. However, numbers are that,,,just numbers.
An example....Years ago I was playing Klipsch speakers(Reference line) through a not lower line HK receiver. Watts and all those numbers seemed compatible. The sound to me (in those days) was pretty good. Then, I got a good deal on a NAD integrated and hooked them up to those Klipsch speakers. Sounded like I threw 3 Army blankets over each speaker. Not wanting to ditch the NAD amp I investigated other speakers. PSB was the final result. I believe the two companies are, or were combined.
The main point here is that no matter how long you compare and try to match numbers, there is no final answer until the speakers and amp together are listened.

Whilst giving a greater choice of amplifier the problem with choosing speakers only above 92dB is that severely limits your choice, of speakers. In the old days our choice of computer was often limited by the amount of storage and RAM today both are cheap.  Today watts are cheap too. A Peachtree Decco 125 will drive anything, sounds very nice too. Go up market and a Naim Nait XS 3 at 70 watts will drive virtually anything, a Cambridge Audio CXA 81 at 80 watts also will at half the price. Speakers at 92dB however choice is limited, Klipsch, not a fan (that's me being diplomatic), Focal may squeeze in at 91 dB ( however they are very bright) others at that rating tend to have horns, think listening to music thru a megaphone and or be very expensive see Tannoy, of course you can have a Zu audio product complete with whizzer at 110dB, great for those who like Harleys but better off with a BMW, Yamaha or Ducati if you actually like motorcycling.  Your are not going to find any from Dynaudio, B+W, or my favourite Audio Physics and many other brands. Pick speakers you like then buy an amp that will power it, plenty of speakers at 86+ dB to choose from, hundreds of amps about to power them.

I'm with Henry. I don't get the obsession with sensitivity, especially when transducer engineers often deliberately choose a lower sensitivity driver set to get improved bandwidth performance.  It should be noted sensitivity is relevant only in passives.  Most actives can play as loud as you care to listen, leaving the efficiency argument behind.