Korea probably has the best general quality in Asia. Not that you can't find better anywhere else if you look hard, but pretty much any Korean factory is good. They've been doing it long enough to be on a second generation, or even third now.
It takes a while for the "hayseeds" from the farm to figure out what's up in a factory job.... and if they staff the whole place, you may have an issue. Korea doesn't generally have that problem, the supervision knows what they are about, and a lot of workers are long-time and quite expert at electronic assembly.
You want folks who have been at it long enough to know what good assembly work looks like..... and QC their own work......... You cannot "inspect-in" the quality.
BTW, the Vietnam Ampeg were made by the SAME Korean company....... just at their Vietnam factory.