We should reject hard-to-drive speakers more often

That a speaker is difficult to drive just means you need to get gear capable of driving it. I think the great majority of people who own such speakers have got suitable power for them. 

Of course that is very true. But like I mentioned earlier, if it were a simple thing to have the speaker be the same but otherwise higher impedance/easier to drive, it would be instantly smoother and more detailed both at the same time since the amplifier would be lower distortion.

This is audible; Steve McCormick makes a very competent solid state amplifier that can easily double power into 4 Ohms as opposed to 8 Ohms. The Anticables guy makes a device called the ZERO that is an autoformer that allows you to drive a 4 Ohm load while the amp sees an 8 Ohm load. He has a letter from Steve that states while Steve's amp can easily drive 4 Ohms, it sounds better driving the same load through the autoformer. I'm sure the autoformer has losses and the like; its pretty good bet that if it were not needed the result would be even better.

That does indeed read like a good bet Ralph.  

Don't know how to explain it; driving our North Creek crossovered B&W Matrix 801 S2 speakers (87dB sensitivity, nominal 6 Ohm with benign phase angles and amplitudes) with only our 100 watt monoblocks (2x6BL7 + 4xKT77) sounds both better...and louder!...than driving the woofers with a Jon Soderberg modified Threshold Stasis 2 (~225 watt/ch.) and the tube amps driving the midrange and tweeters. 

I chalk it up to coherence tricking my brain into thinking it's louder...are there decibel meter apps for smart phones?  No need for responses to that...Google here I come.

Having recently place the Vandersteen Sevens in our Listening Room.  83.5db.  Never would have thought to pair them up with a SET 28wpc stereo amp but there you go, drove the hell out of them.  So you need to try things in order to find what will work in your system.

Happy Listening.

@ bigkidz +1

The theory doesn't always hold true.

I drive my W/P5.1 with Pioneer M-22 2×30 Watt A-Class, sounds amazing.