Highest BUILD quality tube amps?

Another vote for PrimaLuna here. I have a preamp and a pair of monoblocks from them, and the build quality is great. Also love the sound in my system.
PrimaLuna is from the Netherlands, and I believe they're also built there (I think someone earlier was asking about that?)

I am surprised that the Dynaco gear hasn't been mentioned. The ST-70 is still highly sought after. I prefer the improved versions, VTA I believe was mentioned but not in conjunction with Dynaco unless I misread. Anyway, in addition to Roy's amps, Bob Latino has an improved version and for those who are crazy about perfection, you can't go wrong with the variations made by Don Sachs. Roy's improvements over the original are solid, as are Bob Latino's Roy also has his own preamp the SP14 and a phono step up amplifier as well, but Don's DS2 Preamp is a rock solid variant of the SP14 with fantastic components, it's awesome. If reliability is all you are looking for I would go with Roy's ST-70 amp using his octal driver board, and bis autobias circuit.

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.