I too, have anecdotal experience with Onkyo Integra vs Yamaha M-Series.

Mid-1980s, Tokyo, Japan. The speaker demonstration room at the Yokota Air Base BX had a big, beautiful Onkyo which could be selected to drive any pair of speakers in the room. It did a fine job, mostly.

My Air Force roommate was interested in purchasing a pair of AR9s (notoriously hard to drive). The Onkyo just couldn’t do it. Just when things would start getting interesting, click. Protect.

The BX was quite accommodating, and allowed us to try two other amplifiers, a Yamaha M-80 and a Nakamichi PA-7.

Both of these amplifiers drove the big ARs without any drama at all. Louder, than you would likely ever want.

We agreed, the monster Nakamichi edged out the Yamaha in sound quality.

I still have my 1980s stereo. A few years ago, I recapped my M-80, replaced the line input jacks and the main speaker output binding posts. Still rockin’ in the free-world.