Another indicia of quality is whether the amp uses circuit boards, which make assembly less time-consuming and thus cheaper, or discreet transistors which are individually soldered in and thus more time consuming and costly to use ("point-to-point wiring").
A case for point-to-point wiring might be made on the basis of better sonics and lower cost to upgrade or repair.
I believe Thor amps use circuit boards to fix its components, but no signal carrying component is fed through through a printed circuit. The last I knew, Quicksilver tube amps were hand wired.
Cheers,
Tim