No offense, but you know absolutely nothing about what you are speaking of.
1st: Seasonic, FSP and Delta do NOT manufacture in Taiwan. They are merely Taiwan based. In fact, ALL power supplies for ATX/SFX PC's are manufactured
in China. Even factories in Taiwan and Vietnam use "semi-knockdown kits" (SKD) that were initially made in China and only the final assembly is done
off short.
2nd: Seasonic isn't even a tier one. They have great engineering, but PCBA, etc. is all outsourced. Only final assembly is done at Seasonic's CHINA
factory.
3rd: If FSP made a PSU as good as Great Wall, Corsair would use them. But FSP is hung up on their active clamp reset forward topology and until they decide to enter the 21st century and use LLC resonant like everyone else, they're out of contention.
4th: Delta is too focused on producing for white box PSUs for the likes of Dell, etc. You'll note that there hasn't been a Delta made retail unit in
nearly a decade (Antec?)
5th: Great Wall is not "third class". In fact, they're actually a tier one.
All of their manufacturing is done in house. They're actually the largest PSU manufacturer in China.