Low heat alternative to FIRSTWATT J2 ?

@charles1dad 
I'll say it again... 
ALL modern Pass Labs amps use negative feedback. 
The FW amps are a mixed bag. Some have none, some use negative feedback and one uses negative and positive feedback. 

OK, I see you are making the distinction between Pass Labs and Nelson Pass's designs which would include First Watt. No problem. The F. W. are definitely a mixed bag of circuit ideas by him.
charles

Yep. The FW amps are very unusual animals. I LOVE my F5 though, and that IS an amp that runs hot. Base of the sinks hovers just under 60C. It’s warming up right now.

I borrowed a friend's J2 for two weeks and enjoyed it the whole time.  The case gets fairly warm, but, that is, in part, a result of the whole unit being fairly small in size.  In terms of the total amount of heat being radiated by the amp, I only notices that it was slightly more than that of my low-powered pentode tube amps.  

I have also heard that same friend's DIY build of the First Watt SIT amp.  That was a really nice sounding amp too, but, I suspect it puts out even more heat than the J2. 

I don't know of any solid state amps I like over the sound of the two First Watt amps I heard (although I have not looked extensively at solid state amps).  I heard the Devialet and thought it was okay sounding, but, as with the case of solid state amps, it did not hold my interest the way good tube gear does.  The brand of conventional solid state amps that I find to be nice sounding and engaging is Ayre. 

Any suggestion on J2 vs F6 ? I am considering buying one of them for my 93db Tannoys.