Since your question is on BEST BUILD quality and not BEST SOUND quality:
Ayon comes to mind. You could insert the tubes with broken pins the wrong way and it would just blown the fuse and not toast the amp. Insane expensive parts inside. Tube bias barely moved for 3+ years of active use (no need to keep swapping out tubes nor re-bias). Simply amazing. If an idiot can’t break it, nuff said.
I like Rogue 120, 150 and 180 too. But the Apollo ... be careful with tubes blown on you periodically.
There are better sounding tube amps, but they are complete joke in terms of build quality. VAC (never got one that didn’t act up nor service free). Kora. Jadis (try bias them yourself, or accidentally cross the speaker spades, and you’d know exactly what I meant). Modern Carver monos (my buddy’s big expensive red mono blocks kept blowing the tubes away ... and literally set the tubes on fire inside ... not for the faint of heart... yet BC hinted that my friend is an idiot who doesn’t know buy good tubes).
Another big name tube amp maker once claimed that you shall never power up the tube amp without any tube, or the amp would be damaged. Now that’s QUALITY... not!
Most OTL tube amps I owned were fire hazard. They sound gorgeous with the right speakers, but they are also the most temperamental of all tubes amps I ever owned.
What not to consider ever, if you care about quality, that you don’t want fire hazard, that you could walk away for an hour or two with the tube amp unattended, is most mainland China imported tube amps (sorry). You don’t even need to open it up to see what kind of fire hazard is inside. Buy one of them, leave it on, and watch how the bias swings wildly, nuff said. (and I am talking about the *expensive* ones costing $2k-$5k MSRP)
