I can’t tell you how the Ampzilla will compare to the McIntosh amp, but they are very good. I have owned many amps in that price range and the Ampzilla is one of the best. It’s nice that they are cool running and can deliver the amount of power they do without having to have a 20 amp outlet. They provide great detail and dynamics. I think they will tick the boxes for the things you mentioned you like, except maybe the "airy" high. I’m not sure I would describe it that way. I think the treble response is pretty neutral. To me, "airy" means something artificial added to the sound, but adjectives can be misinterpreted.
There is a lot of owner feedback that you can find with a search. I don’t remember reading anything negative about them before I bought mine.