The high degree of differences between amplifiers has always surprised me. 'A straight wire with gain' - not. I am not an electrical engineer but I would expect a lot less variance than with electro-mechanical components like speakers, cartridges and microphones.
That said, for my ears Krell any day. But from the D'Agostino days, not the private equity people, please. The 1980s pure Class A are the best, sadly no longer made because of wimpy environmental issues. My KRS200 References were modified to issue 400W per side (not Japanese watts, and doubles up, down to 2 ohms), but consume nearly 2kW per side. No-one gets something for nothing.