Highest BUILD quality tube amps?

There's a number of them that are very high quality and low maintenance.
VAC, Atma-Sphere, BAT, Lamm, Music Reference, Herron, VTL, Rogue all qualify IMHO. Audio Research is one of the biggest brands, but while they certainly have a large number of fans, I have heard plenty of stories and had one personal experience where they are a step down in reliability (and repair cost) vs. those mentioned above. 
The Air Tight I once owned was also trouble free, but my read is that there aren't too many sold so it's hard to get a meaningful sample. Cheers,
Spencer

Will Vincent (autospec) specializes in rebuilds of Dyna ST70's. He built me a really nice SET 45 on a Dyna chassis! Recommended!

Manley Laboratories; they make their own trannies too!

Prima Luna has got my attention for the simple reason of point to point wiring. Circuit boards are only so good IMO. Boards do have a range of quality as far as material used, thickness of traces, etc. In the end though, it is hard to beat point to point.

Atma-Sphere for me.
B