Tubegroover,
Allan is a great guy. I have appreciated his advice and expertise over the years.
I have modified the ZH270 by bypassing the volume pot, adding Stillpoints standoffs to the circuit board, silver wire upgrade, cap upgrade and bypassed the A/B switch. I don't have the Stillpoints feet yet but that is next. It is a great amp and the only other amp I will buy is another Berning.
I am going to purchase the mono version of the ZH230 class A amp as soon as I can. My only concern with that is how it will mate with a 90db speaker.