Why Don't We See More High Current Electronics?

Ooooo . . . I've been summoned, like Notorious B.I.G.!
http://www.southparkstudios.com/clips/155324/the-ghost-of-biggie
Actually Al, you're correct save a small arithmetic error. A "pure voltage source" amplifier that clips at 100W into 8 ohms of course puts out a maximum of approximately 40 volts peak-to-peak before clipping, regardless of the input waveform or load impedance. So for the combination of two equal-amplitude sine waves at 4KC and 40C, that's 20V peak-to-peak for each before clipping, or 14.14VRMS each . . . corresponding to about 12.5 watts RMS at 16 ohms, and 25 watts RMS at 8 ohms, or each at 1/4 the rated power like you said. To some, these numbers might seem like a large amount of "loss", but this waveform into even a low-sensitivity domestic loudspeaker would be absolutely ear-splitting (and probably tweeter-frying in short order).

But to comment on the thread . . . this is some REALLY well-trodden ground. Please see:
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1258580057

I have two main points of contention with Atmasphere's "white paper" to which he frequently links. The first is simply the lack of citation of any historical or scholarly references, or measurement data. This need not be . . . I think that Atmasphere could actually support his design choices much better by a properly researched, documented, and peer-reviewed paper on the subject.

The second is the interchangability of pespectives on amplifier output power ratings, output impedance, and circuit design, specifically the use of negative feedback. Obviously, Atmasphere prefers Class A OTL designs with little loop feedback . . . and the consequences are very poor power efficiency and a high output impedance, both of which are key factors in the rated power outputs of Atmasphere amplifiers.

The wholly illogical part is the inherent value judgement against amplifiers that have clipping-power-versus-impedance characteristics that are different from Atmaspheres'. Because an examination of this data gives ZERO information about how much current an amplifier will produce, what its output impedance is, or the amplitude of any distortion products in its output.

So to answer the original poster's question . . . there are plenty of high-current amplifiers on the market. However, you can't tell which ones they are by examining the clipping-power ratings into various load impedances.

Ooops, Al, you're correct. Didn't see the 4-ohm bit . . . blasted eyes!

Fitting your criteria, I really liked the Moon W5 in sound, build quality, and bench performance when I had one on loan. The Bryston 3BSST is also a nice amp.

The McIntosh MC7200 might also work, but their input impedances are usually like 22k. BTW it's a high current amp with a low output impedance, which can't be inferred from it's specs that don't "double down". It's continuous power output into lower impedances is limited by the power supply . . . but that's not really a criticism, as there's still a ton of power available, and lots of dynamic headroom.