If you want an amp with crazy amounts of power, check out the MC7200 instead. It, unlike the other two, doesn't have autoformers and so its power output essentially doubles with a halving of impedance. I love mine.
McIntosh feels that Class AB push-pull is best and so all their amps are this way.
The gain controls are actually more useful than you may think, as Bigjoe alluded to. They make gain matching with a preamp's volume control very easy and give you balance capability if your preamp doesn't have it (like mine). Good luck! Arthur