Most high-quality loudspeakers are 4-Ohms

Nope. But you knew that, didn't you :)?

Stan said it well.

Count all the two ways, or book shelfs and the figures get more in line to higher impedances.

To my ears, most high-quality loudspeakers are lower impedance loads.

If you are only used to listening to systems driven by big, high current SS amps, you might that it is true. Many good, multi-driver speakers that mate well with SS amps have low impedences. However, there are many very, very good speakers with high impedences. They tend to mate well w tube amps. See for example, Vandersteen, Merlin, Coincident, Silverline, Classic Audio Reproductions, Dali Megaline, Horning, Audionote.

Swampwalker, I don't consider the Vandersteens to be high impedance speakers and there the only ones of those that you've suggested that I've heard and appreciate. While I haven't heard them all, some of the other I down right dislike. But, that's just me, YMMV.