How hot is hot when moving from class a/b to to a or tubes?


I am considering moving from a class a/b Luxman L509x to a class a or tube amp. 
I have never owned a class a or tube amp, so have no experience of living with one. My kids are hopefully old enough and wise enough not to burn themselves, but I do live in an already warm house with bifold doors leading to a south facing garden. There is no escaping the sun, despite having uv treated glass. 
 
My room is roughly 9 meters by 12 open planed living space. Equipment is, Luxman L-509x integrated, Zu union 6 supreme, 99db sensitivity (this is why I am considering a lower powered tube I can barely turn the Luxman up) music is played roughly 6 hours a day, more on weekends  

who here has moved from class a/b and d to class a with or without tubes. What were the differences of things like:

warming up time 

additional heat to the home

Running in summer time 

additional cost to run

any considerations I should make before purchasing something. I will try in my home, but will need to free up funds 
 

 

mpoll1

FWIW, I live in Texas where it gets pretty hot, after going from a set of B&K M140s then a CJ MF2250A both solid state to tube monos by different companies including VTL & Quicksilver & a Pass Labs XA30.5 the heat issue never was a problem till I hooked up a Jolida 302BRC and there was no way I would run that amp inside a cabinet even with proper ventilation due to the heat exchange. The moral of the story is be diligent because they are not all created equal and some will have that as an issue. Enjoy the music

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@blisshifi  thanks for that. Yeah I don’t feel I am getting what I can from these Zu’s. I will take a look at some of those. It’s close to 9ft away from the amp, so good shout there.