Most high-quality loudspeakers are 4-Ohms

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

Well, sort of, but was not quite sure. ;) I had it direct quoted from somewhere without much context. How about "there are more high end speakers with 4 ohm than 8 ohm?"

When I had relatively cheap amps, I could not find anywhere about power ratings (RMS) mentioned for 4 ohm in their specs. All were listed for 8 ohm.
Most mid-high end power amps seem to have ratings listed for both 4 ohm and 8 ohm.
Most relatively cheap speakers I had (including Klipsch KLF-20, B&W 603 S3, Celestion Impact 20, ...) were all 8 ohms.

So, I was wondering if the low impedance has to do with high end speaker design in general. Of couser, I agree that there are many high end/high quality speakers with 8 ohm, so there must be exceptions.

high quality is relative. There a number of so called "high quality", speakers (4 ohms) that sound like a piece of sh%^*

Unsound- OP was, I thought, talking about 4 ohm nominal vs anything higher. See for example, his recent response:

When I had relatively cheap amps, I could not find anywhere about power ratings (RMS) mentioned for 4 ohm in their specs. All were listed for 8 ohm.

In that context, Vandersteens are mostly spec'd, IIRC, as 6 ohm minimum and would qualify as higher impedance (i.e., higher than 4 ohm) loudspeakers. Of course, you and I could disagree about lots of things audio, but I don't think that we would disagree that the speaker makers I put forward are generally considered "high end".

And to the OP, the post I quoted is very telling. What you are seeing is that in-expensive solid state amplifiers often lack the robust power supplies necessary to allow them to deliver high quality specs into a 4 ohm or lower load (many speakers exhibit lower than spec'd impedance across at least a part of the audio spectrum).

Any 4 ohm little monitors out there that can out do the 15 ohm Rogers LS3/5.♫

Swampwalker, I suppose for the most part we actually do agree. The Vandersteens aside from their selfpowered subs have a minimum impedance range of 2 to 5 Ohms. As for the others, yes they are generally considered "high end". I just haven't heard any high minimum impedance speakers that I would care to own, so IMHO I guess I wouldn't consider them "high quality" regardless of the craftsmanship, marketing, etc. involved. Others are of course welcome to disagree. I think the OP's question has more merit than some might at first assume.