My personal experience with Adcom has been really bad.
I purchased a Adcom 5300 in 2001-2 to power some Martin Logans Aerius i. The amp was always used at low to moderate levels (8 to 10 max on the preamp volume knob).
The amp was getting so hot, you could barely put your hand on the top cover. I could have use it to cook.
Same with B&Ws speakers.
Same, and I can understand, with Magnepan, eventhough it was marketed as a tough beefy amp capable of driving any load with huge power reserves. I have sent the amp 3 times for repair. I have never been able to keep this amp running more than 3 weeks without issues. The third time, Adcom sent me a new unit. 3 weeks later, it gave up. I did not want to send it back a fourth time. And Adcom were so proud of themselves that they propose to take back the 5300 and sell me a 5400 30% off! I certainly did not want to heat my house with a 5400.
So I took the 5300 to the dump and the only regret I have is to have paid probably around $400-500 for it back then.
My guess is that in the late 90s Adcom took a gamble and got their stuff manufactured in China where consistent quality was non-existent at the time. Or worse there was a huge error in the 5300 design, which would demonstrate that Audio and amplification is really not what Adcom should do.