Pass Labs x250.8 vs tube amps


I have a beautiful system. Lumin X1 > BAT Rex 2 pre > Pass Labs x250.8> Sound Labs M545 (ESL) in a tiny room (9x 11 ft).  This system has the most glorious SQ: smooth, detailed and powerful , along with great bass. I would say this sound equals or betters any ultra high end system. HOWEVER, I have a problem. My system takes 6 hours of music playing to sound this good. I had X250.5 and I had the same issue. Leaving it on idle overnight doesn’t solve the problem. It is 15 W class A, so it generates quite a bit of heat, and yet I have to still play music. Because my room is small, I don’t crank up too much- maybe this is the problem, but the temperature doesn’t complete stabilize for 5-6 hours. The top reaches 107 deg in 2 hours, but the front plate doesn’t reach 107 until the 6 th hr when it starts to sound glorious. I have never had a tube amp and I am wondering if I can reach that thermal equilibrium and the glorious SQ faster with a tube amp? I worried about the heat generation with a tube amp in this small room, but X250.8 generates 450 W just idling. This is no worse than tube amps like Audio Research 150 Se, which I demo’d and was impressed by. BTW, I need power in the amp because of the esl speakers.
What do you all think?

128x128chungjh
I own an X250.8. I have had tube amps in the past- CJ and Rouge 

2 comments- my amp is fully warmed up in 1 hour. Next- having had tube amps for about a dozen years, with the X250.8, I do not miss the tubes at all 
Since you have the BAT Rex pre, maybe you should consider a BAT power amp like the VK 255se. Yes it's class AB but it has plenty of power for your panels. I have Apogee ribbons running on a BAT VK 42se pre and the BAT VK 250 amp. Great balanced combo.
@ chungjh 

the main switch on the back is always left on; the switch on the front is turned off after a listening session