MAC Autoformers?

I'm not even sure what the autoformer does. It seems like an effort to provide the same level of power no matter what the impedance load of the speaker is - which in theory sounds like a good thing. But I don't understand much of this. I did not know there was controversy regarding autoformers - so I wait to be enlightened in the issue here.

You have to admit this is confusing. Now it seems that Mac uses the autoformers in the "higher end" units. Why would the do that if it hurt performance? I can't imagine they don't have technical competence and the autoformer is some kind of bandaid for inferior SS design chops. Aball, where are you?

The reason I though the autoformer was a good thing is that my speaker manufacturer (Merlin)suggested that if I want to add an SS am (I own two tube amps that I switch around)to consider the MacIntosh with the autoformers, which is interesting in light of some of what has been said here in that they have a very easy load and very smooth impedance curve, where the autoformer would seem to be less needed. Well I think I'm going to decide based ergonomics and not worry too much about the AF/non-AF issue. Any opinions on differences in sound quality, or other considerations between the 6300, 6500, and 6600. Power is not an issue, my speakers run perfectly fine on 50 watts or more.