There was one significant operational difference, which others have confirmed. I don’t know why this is true, but the Class D amps needed 2-4 days to warm up. The Luxman needs no time at all. I have no rational, engineering explanation for this. After leaving the ICEPower amps off for a weekend, they sounded pretty low fi. Took 2 days to come back. I can come home after work and turn the Luxman on and it sounds great from the first moment.
Just a guess, but the switching times of transistors vary as a function of temperature, which may take a relatively long time to stabilize in a class D amp due to the low power consumption. And perhaps what is occurring during the 2 to 4 days is that the turn-on and turn-off times of the transistors which supply current to the output from the positive DC rail become more closely aligned with the corresponding switching times of the transistors which supply current to the output from the negative DC rail. Thereby reducing or eliminating "shoot-through" or "dead time" that may occur during those transitions, when both groups of transistors may for a brief instant be simultaneously on or simultaneously off.
On another note, Erik, as others have said thanks for yet another very interesting thread.
Best regards,
-- Al