Yes, when JC1 is switched into high bias mode, it becomes very warm.Not to me they become invisible like the speakers have left the room, and the music just washes over you in a 3D sound stage, that you swear you can get up and walk into.
And I've built many, some very big ones over the last 30 years, even a self contained 120w-8ohm pure class-A water cooled one that could double down to 2ohm, that was two man lift, the size of a coffee table.