Highest BUILD quality tube amps?

Conrad-Johnson. I’m surprised there is so little mention here. I’ve owned their products for more than thirty years with no problems whatsoever.
The availability of service is a huge issue for some of these brands. c-j will service anything they’ve ever made, not so with many including Audio Research. All hand wired here in Virginia. Extremely high quality parts throughout... an important part of their value proposition. And due to theses factors, c-j products retain their resale value. Oh yes, they sound amazing as well. In fact, when I was upgrading some years ago, Lew Johnson bought my old EF1 phono preamp for his own use.

I have had VTL MB-450 Series III for many years with no service required.  They sound great and with the Auto Bias function you just turn them on and listen......

MC275 still and always is a great amp...Some build quality issues popping up with McIntosh over the last 10 years or so. I loved the sound and features of my 220 pre but it had tube socket and software issues. It would turn off and not respond to the remote or front panel controls a few times a month, just random, you didn’t know when it would occur, so I finally let it go.

Not the prettiest in the room but another + for Decware. 

I do use a sub in my system, I love deep bass...just a preference of mine. I was worried about bass with tube amps, however someone told me since I use a sub, I can always adjust the levels for whatever tube amp I get and get SS deep bass