Highest BUILD quality tube amps?

Quicksilver Audio is built among the best out there IMHO. I have a slew of Mike Sander's gear and never a problem, Many of my Audiophile friends have his gear too. All problem free. Also, Call them and you will be speaking with the man himself. As I write this, I am listening to his Integrated amp in my office. Very nice piece.

I love my Conrad Johnson LP260M SE's.  They sound great, rarely have to change a single output tube (once a year), and have never had a problem with the unit itself.  CJ dealers talk about a 97% reliability rate (no trips back for repair)-- and I believe that number.

Another advantage of P to P wired ( NO pcb's) tube amps is they are easier to diagnos and repair without a schematic diagram. So if you need to have it repaired you can take it to a good local guitar amp repair tech.

Plus 1 on Prima Luna Dialogue Premium and the HP power amp, assembled in China. Also BAT. Check out the videos that Kevin Deal does on BAT and Prima Luna at Upscale Audio. I have noticed that only one person has mentioned Conrad-Johnson. Superior build and they last forever. I have one that is 35 years old and still thumping.
Rollin

I have a McIntosh MC275 now and it is a monster in every way. The only flaw is the lettering on the sides as it always seems to rub off when you lift up the unit. 

Before that I used a pair of MC30s for nearly 20 years. I bought them used from the estate of the original owner, who told me he used it everyday and was sure he had never once replaced a tube. He had them from 1961 to 1993. Crazy. And I hooked them up and enjoyed the hell out of them for another 8 years before I bought new tubes.

Anyway, hope that answers your build question!