Moving this over here, where the bulk of the discourse is applicable:
I would agree with most of what you stated, and would modify to say that level of acceptable noise is subjective.
I believe an amp of considerable cost, deemed high quality at a minimum should not have to be constantly tweaked to find an acceptable level of noise to enjoy listening. For example on the DNA Stratus or Starlett, both amps do not suffer from these type of noise issues nor involve any special power strip or DC offset filter. Both these amps are near equivalent in price point to the Pendant and Mogwai SE, granted the Mogwai SE and the other amps higher up the ampandsound line have speaker taps it is not an apple to apples comparison.
The point being is folks should be aware of the noise issue ahead of time, rather than finding out after the fact. Some commentary around using a lower ohm tap, or they are perfect with ZMF headphones, those are complete subjective and user driven decisions. Not all of us are going to agree on those particular things, and that is okay. It should be discussed openly, just as any component/product should be discussed openly.
The moment we jump into a groupthink mentality, the purpose of this conversations across these posts turns into fanboyism and meaningful information is left to the wayside.