I have owned M60s for 17 years. I first purchased them as a kit, and then I had them upgraded in 2007. I have changed the tubes once in all that time. They were absolutely reliable even though I drove some difficult loads with them. I used them to drive my Quad 2805s. I also want to say that heat has never been an issue. The 100W Wavestream Kenetics Boxters that I am using now to the drive the Quads generate much much more heat. They are standard push-pull amps based on 4 6550s (KT88s) each.
Atmasphere amps trustable?
Tube world, a big world, then I came acorss the Atmasphere on the net, looks different from those common tube stuff... kinda weird, the M-60 uses 8x 6AS7G output tube and 4x 6SN7 driver tube per channel, where're the rectifier tubes? Plus they're so-called OTL, sounds even more weird.