Yep, they get warm but with A/C register on the floor blowing cool air into my amp its good to go.
Mine goes all the way to 14. Tubes that is. 2 matched Quads of KT88's and 6 x 12AU7's
2 matched quads of 150's may be in my future. I'll set the thermostat to 59 degrees, that should do it.
Don't have these any more (and not my picture), but these 32 tubes put out surprisingly little heat collectively. It was fun matching up 24 output tubes though.
PS: Do I win with 32?