I have a couple of MBL monoblocks purchased used, model N15.
They clearly sounded better than my ARC Ref 160Ms, even after tube rolling, vibration treatment and good power chords. It took some burn in time to get rid of the traces of class D sound signature but now they sound like a very good AB class amp. They are efficient, powerful and never get hot. Only adjust I had to make in my system was using good copper wire.