Amps that don’t impersonate space heaters.

I used to run a BAT VK55SE amp and loved the sound, but couldn't bear the high temps in the summer. I picked up a pair of Atmasphere Class D monoblocks prior to last summer and haven't looked back. Much as it bothers me, I never put the BAT back in service during the 'dark season' as the Atmasphere Class D amps just sound too good to put on the shelf.

I'm running them with a BAT VK33SE preamp, into a pair of Raidho X1 monitors, in a studio-like (i.e. very near field) setup and absolutely love the sound. 

Per his comment above, I'm in the same camp as Ralph: The sound the Atma Class D amps put out has everything I need to enjoy hours of listening, deep into the music, and without fatigue. The fact of them running with virtually no heat is but a mere side benefit.

GanFet or Class A (sliding bias tech) SS amps

Class A done well has special qualities that seem to come at a price. Only tubes seem to extract a similar price, thermally. I can suggest a couple of options:

Combine a tube section preamp with a well-designed Class D (e.g., a ProJect Pre Box RS2 Digital and a NAD C298).

Use a modern GaN FET amp: Peachtree’s Carina GaN for example.

Use a hybrid amp with partial class A topology, NuPrime IDA-8 is compact and is a Class A- Class D hybrid which has been a successful model in that company’s lineup.

Your horns should do well with any of them.

@ghdprentice Thank you for the succinct description of high quality bass reproduction. I loved my slam back in my younger days, and noticed that it disappeared as I got into better gear, to be replaced by a more complete reproduction of the music. The nuance in the low frequencies is one of the best parts of a quality system. 

Seconding the Atma Class D's. Tube amps and A/B amps just roasted me in my hot and small upstairs bedroom. Atma's solved that issue with zero heat and they don't even get warm. I don't think I'll ever be selling them.