recommendations for amplifiers that don't emit tons of heat

Thanks for your responses! I'll check out that link.

In the meantime...

Kenny, I have and audio research ls27 preamp and paradigm studio 40 v4 speakers. The room is 8x10, and it's lined with shelves of records, making it even smaller. No room for floor standing speakers, and placement is suboptimal. I realize such a small room has limited potential, but all the upgrades have been fruitful so far, and I've also bought keeping a future space change in mind. So while I need something that sounds good with the studio 40's, there will likely be a speaker change at some point and I want an amp that can handle bigger speakers.

I always buy used and my budget is $2000

And I listen to a very wide range of music. I’m a jazz drummer so the drums need to sound real!!! But in addition to jazz I also listen to Indian music, European classical, African drumming, korean music, indie rock, etc at mostly moderate levels.

Cmach, do you have any experience with Audio Research, Krell, Bryston, or Aragon? If so, how does the McCormack compare?

I realize there are tons of variables, but any information is helpful. 

@tripg 
McCormack's have a very good sound at a very good price. SMc Audio will perform upgrades that will bring them to current standards, too.
The DNA-1 I owned didn't put out that much heat, either. It was warm, but not a space heater like my Atma amps-which I love to death.
What are your power needs/speaker? It would help in giving you a recommendation.
Bob

@gdnrbob
Paradigm studio 40... but hopefully I’ll be in a larger space in which I could use floorstanding speakers in the next few years