Class "D" amp? I do not have a clue. Do you?

Kij has it correct. The RDon is very low for MOSFETs. Resistance Device on.
This is a big selling point for discrete power devices. less resistance is less power lost, or rather delivered to the load.....whichever you prefer.

Now, on to the full /half bridge argument.
http://www.irf.com/product-info/audio/classdtutorial.pdf

Above is the Internation Rectifier article on 'd' amps. Very good read. But, this is only part 1 of 2.
The full/half bridge configurations are well covered as are some of the rf issues.

QUESTION: how do the 2 different kilowatt Bel Canto amps differ? Don't they both use the B+O ASP module? Is there only a difference in input circuitry or the Zobel?

Here is a link to the B+O ASP site.
http://www.icepower.bang-olufsen.com/files/solutions/icepower500asp.pdf

Looking at the technical specs you will see the power output is specified for 60 seconds.....not FTC continuous. The ASP1000 module has only a 30 second time limit.

I like my 'd' amp. No question about it getting the job done.

Kij, How DID you know my speaker wires were 197 feet long? Just kidding!

As for the PS switching noise at the output, that is removed with the low pass Zobel. However, there are special filters used by the measurement crowd which test equipment. Some problems occur when measuring 'd' amps.

Kij,
I gave up listening to sine waves sometime soon after I survived the '70s.
Zobel limit on long term power is therefore pretty much a non-starter.

One other MINOR issue, I don't think yet mentioned, of 'd' /ICE is that the frequency response changes as a function of speaker impedance. Lower impedance starts rolloff earlier. The ASP1000 module is worst in this respect being what....about 1/2 db down at 20khz w/4 ohm load?
Give up, at least for now, the idea of flat, wide band response out to X-ray.

One other 'd' player I've NOT seen mentioned.

International Rectifier has several 'd' amps out there. I've got a reference sample for test. I need to build a power supply so I need a transformer / caps / rectifier for a basic one.

http://www.irf.com/technical-info/refdesigns/audiokits.html

Anyone try any of these?