There's just not much out there anymore from 'the big boys' (Peavey included) that is NOT made to be disposable. The guitar amp world has a plethora of boutique amp and pedal builders who focus on quality first, but they all seem afraid of dropping an octave. You can probably count the number of custom bass amp builders out there on one hand. And that's going to be the only way you're going to find something new that you know will be able to be serviced and isn't going to be built around an output transistor board that is discontinued before the amp even gets to market (cough Markbass).
Mesa is probably the only major manufacturer still doing old-style serviceable amps, and I'll bet their QC is much better now that they dropped Guitar Center, but I gotta say, I've never been overly impressed with their quality. They have lots of problems in areas where they shouldn't, BUT the huge caveat about that is that most of the ones I saw were during their heaviest GC-ordering era over a decade ago. I bought a used Bass 400+ about five years ago and have never had to do a thing to it and it's running fine.
Traynor has great support, but their QC has REALLY dropped in recent years as they've had to cut costs to compete. I'd trust their warranty though.
Surface mount stuff also brings another factor into play: schematic values may say one thing, but in the Asian factories where this stuff is made, it means next to nothing and the parts themselves, even when they DO match a circuit diagram, have such tight tolerances that literally unless you find one of the same components out of the same batch of any components from which the amp was originally made, replacing a single defective part is impossible because the entire board was "tuned" to work in the factory that built it and without knowing where the variations in the actual values occurred (tolerance) the stuff will NEVER work right.
At the TV station where I used to work, we had to TOSS a multi-thousand dollar power supply for the satellite truck uplink literally because of a .001 cent SMT resistor bank that could NOT be repaired. We tried, and these are guys that deal in this stuff every day, not just me, the vintage snob. It pissed all of us off and we all took turns troubleshooting and tracing the circuit. We FOUND the problem and the bad parts, but because of the tolerances in the rest of the other boards, replacing the defective parts with ones of the same value only caused other problems elsewhere. I have what's left of it in my garage where I cannibalize it.