It must stay nice and toasty in that room! On the other end of the spectrum, I'm really impressed with these modern switched power amps. Those amps are not really 'digital' (though often called that), even though they switch between two states (positive and negative power supply rails - binary output levels) they use some form of pulse-width modulation, and that pule-width is a continuously variable analog value. Efficiencies of 100% theoretical, above 90% in practice. Very tiny and lightweight relative to the power out.
-ERD50
Yes, it is toasty after a while...great for the NJ winters, in the summer AC fixes the heat issue. ;-) The filaments of the big tubes each burn 100W just to light up (10V@10A), then you have the dissipation of the high voltage at 330W per power tube plus 6W for the driver tube in each amp. So you're talking 436W per amp not counting any other losses.
I owned a couple of the highly-rated Class D switching amps, before I decided to build my own using tubes. They sounded good, but didn't pull me into the music the way I thought they should. Definitely not as good to my ears as a good tube amp, IMO.
In any case, it was a fun project and definitely makes for a good talking point at dinner parties.