Tube cage on or off during use

I can't see how it would make a difference. I'd leave it off if you don't have kids or animals that might touch it.

Tube cages are really designed to keep someone or something from getting burned from touching the tubes. Some enhance the looks also. If safety is no concern then just go with what looks better to you.

Some tube cages do vibrate when placed close to the transducers, but most quality amps such as the TAD should not be a problem.

Thanks for the Pearl Coolers tip, Listener57. I'll have to weigh my appreciation of nudes against heat-wicking covers.