Csontos and Ralph,
So, if I'm understanding what you're saying, some amps sound better cold than when they're warmed up? If that is the case, anyway it goes, it seems that a person needs to leave the amp on and accept the way it sounds warm.
That is, unless you want to listen for an hour, turn it off, let it get cold again and then turn it back on and listen for another hour. That just doesn't seem to be an ideal way to listen to your system.
If a warm amp is at least consistent even if it doesn't sound as good, at least you have a known sound that you can count on.
Am I thinking wrong?
Chuck