Like Sfar, I can't add to the technical side of this discussion but I will tell you that, IME, in my system, there are 2 extremes in tube amp heat production. Coolest running is the Berning ZH-270. Hottest are Joule OTLs using 8, 10, 12, 16 of those big ole beautiful Russian 6CC3Bs. With some trepidation to be contradicting Atmasphere, in that case, the output transformers, being absent, have nothing to do w it. Those tubes are just little furnaces; even the Almarro 318s that use only a pair can heat a room!
I suspect that those examples are outliers with good technical reasons for being so. The difference is night and day (or winter and summer). In general, I'd stick w the advice you've gotten above. But, I will say that if I lived in the south, I'd probably never have sold my ZH-270. Out of production, so hard to find, expensive ($4-5K), and not compatible w all speakers, but probably the best tube amp I can think of for your situation. A less expensive but also hard to find option might be a high eff speaker w Berning's Microzotl, which uses a pair of 6SN7s as output tubes!! In a small room at my house at the beach, that little amp sounded pretty darn impressive driving a pair of 96 dB back-loaded horns. Now my taste runs to singer-songwriter/fold/acoustic type music at moderate SPLs, but in the right circumstances, it might be option. They show up here from time to time at just under $1K; since they were primarily marketed as a headphone amp, you might have better luck looking for one on head-fi.org. Good luck, have fun, and stay away from those nasty transistors ;-)
