Jadis orchestra reference or DA50 for Proac D15?

All tube amps get hot and generate a lot of heat, same with Class A solid state amps. However, these "small" integrated Jadis amps like Orchestra and DA50 are quite tolerable in heat generation. You will only notice the heat if you put your hand close enough to the tubes.

With regard to whether it will be enough to drive a Proac D15, I think it should be okay since it is a "small" two way floor-standing speaker, with a 6 1/2 inch mid-bass driver.

I used to have Jadis Orchestra Reference and now currently have the DA50 Signature. The DA50 is definitely a big upgrade to Orchestra in every way. I use these integrated amps on my Rogers LS3/5a, and despite the small size of these speakers, they are hard to drive to make them really sing. The Orchestra did the job, but DA50 did the job with a lot more ease and sounded much better!