My XA 30.8 doesn’t produce the heat my 300B mono blocks do and in either case the heat produced in minimal. The joy of hearing what the 30.8 brings to my listening sessions far outweighs any concerns or perceptions about it producing heat. If you are inclined to try Pass Labs I encourage you to!
Disclaimer: as you read the following, know that we’re Pass Labs dealers.
I have similar experiences with our Pass XA-25. It puts out quite a bit less heat than our NiWatt 300B amps do.
Having said that, more output devices (more power) = more heat. The question becomes how much is too much, and what your alternatives are.
If you were to go with a large tube amplifier with a bank of KT-88s, then you’ll also be putting out a lot of heat.
If you go for a class A/B design, there are sonic compromises. Of course, if your amp runs mostly in class-A (like Pass’ "X" series) before switching over, then you can sidestep these issues for the most part.
I have no experience with class-D amplifiers.
When you get to the point of considering a ~300 watt amplfier, it’s time to ask yourself some questions. Is it time to consider a speaker swap?
We do our best here at Galibier to expose audiophiles to the joys of high efficiency speakers - smaller amplfiers, with less dyanmic compression, and the thing no one seems to mention about high efficiency speakers: late night listening at lower volume levels becomes more satisfying. It's not just about loudness per watt.
Thom @ Galibier