Believe me.......first off amps dont produce sound, their job is to amplify a signal and not let in noise or distortion in the process- most amps produce a level of 'coloration' (which is basically distortion) which is what people claim to be a different sound from using diff amps
As far as higher end amps go- they have higher damping factors and can control the reactive nature of speakers better , keeping them from producing distortion into the sound-
higher damping also is key to keeping the amp from loosing speaker control and maintaining lower distortion levels at lower impedances
Also you are paying for better efficiency, higher grade componentry and power supply, greater build quality
As far as Richard Clark goes, no one may be able to take 10G's from him- but who gives a crap- i trust my own ears, I want to run high grade stuff for my personal preference- and that makes me happy
You can run any of those amps you mentioned, and achieve great sound
People that want a McIntosh are people that know what they are looking for- Same for Tru, Zapco, Arc, Brax,,,etc....whatnot- they aren't debating the 'watt is watt' theory- if thats the case we'd all be running Lanzars