My audio experience is quiet extensive, going back some 30 years before I was a partner in Audio Tweakers in the early 2000s.
If you understood why your subjective opinions and experiences mean nothing to anyone outside of yourself perhaps you wouldn't post this logical fallacy called an appeal to authority, in this case your own.
Read carefully what @atmasphere has written.
Sure, you can trust your own ears, and ignore the measurements and science, that's fine for you. The problem is there is no reason for me nor anyone else to trust your ears.
Like it or not, an amplifier is defined asa device that increases the amplitude of a signal as high in fidelity as possible. We can use science to evaluate its performance as an amplifier. Some people want a wire with gain. Others prefer sweet distortion. To each his own. When an amplifier fails in a gross way to achieve it's design objective due to variable frequency response with load, it's not a good amplifier. It may make you happy, but it's not a good amplifier by definition.
As to the tweaks that can't be measured or substantiated in any scientific or objective way, they are fraud, pure and simple. If you and others want to shell out money and support the charlatans who are all too happy to take your money, please feel free to continue to prove PT Barnum correct, as so many others have.