Hello,
I'm getting the mch-k38 and I wondered if it would be suitable for this amplifier to sit underneath a receiver (Marantz SR 7011).
I understand the amplifier manual suggests a minimum of 4 inches. I would understand this concept if this were a class AB amplifier but doesn't the Nuprime run cool enough that you could stack things on top of it?
Thanks in advance!

Most always it is a good idea to NOT place other components on top of any amp.
That said, the K-38 is slightly different than the other NuPRIME amps in that it has "ventilation openings" (vents) on top of the chassis.
I have several components stacked on top of mine, BUT. . .I have 1.5" rubber feet (Parts Express) BOTH underneath the K-38 and on top, so that airflow is free and easy.
I leave it on 24/7 and just went out to check the temp. To the touch it is just "warm".
However, I WOULD NOT suggest doing the same without the same cautionary use of the rubber feet (which also act as a vibration damping measure) on the top and bottom.
You might also consider setting up your IDA-16 in such a way as to employ it BOTH in your HT set up and as a SEPARATE High End 2 channel system.