The Suggie does get warm but not hot, and I would suggest it needs some ventilation but Sugden may be able to direct you better to how well they work in cabinets.
If you want to listen you'd be very welcome, I'm in Blackburn
Sorry I've taken a few days getting back to you.
I really love the combination of the sugden with the Harbeths, having said that I don't have a huge experience of using multiple other amplifiers with them. Alan Shaw would be keen to point out that they work well with any well designed amplifier, but my feeling is that they are very highly revealing of what is upstream from them.
I have used previously with them Rothwell amplification (stepped attenuator pre and MOSFET monoblocks) gorgeous with well recorded material but dreadful with anything mainstream. I have also had a go with base model creek amplification, lovely little amplifiers but the Suggie really projects a much bigger sound stage.
The biggest changes were with sources, moving up the Sugden CD player chain made massive differences and going from CD21se to Masterclass has taken away lots of the upgraditis........