Boards are so cheap and easy to make that I'd bet most manufacturers are using their own designs. You could order LM301's on Digikey for 10c each and have a US board made for like $5 and solder up your own Quantum for less than what you could buy it for from AliBaba, delivered of course. So, everyone wants all that margin for themselves, because each time you have someone make something you can make, you're losing margin. Anyway, China stuff is difficult because there are a thousand "chingchong" (which is shitty, btw) manufacturers and we're not familiar enough with them to know which are good and which are bad, same as with any product. Kingbrite seems to have made a good name for themselves. That's who I'd buy from.