Unfortunately, my experience with my M-60 was not all that great. I bought it new about 4 years ago through an authorized dealer. Within the first 3 months, 3 output tube failures. Every time a tube failed, I would hear a loud pop through my speakers scaring the c***p out of me. Tube hiss was another issue. Power transformer hum was another. By far the noisiest tube amp I've owned. After 6 months, I sold it and never looked back.
On the positive side, it had the best high frequency I've ever heard from any amp. Smooth, crystal clear, and detailed.