Good to know you did try, and thanks! Tuning piano using tuning forks is very different, those are pure tones! It also is proof to you that frequency response is the main factor, you basically tune for frequency, not much else. Different pianos will have different harmonics, but how many/often concert goers would say different pianos in different concert halls sounded different to them, surely they sound different, but the
overwhelming influence/enjoyment is the music itself, that's the focus. The frequency response between 20-20,000 Hz, the well established audible range for humans are typically ruler flat for almost all amps at the level of mid range AVRs and "separate" preamps and power amps.
So when their total harmonic distortions plus noise are also well below well accepted below the threshold of audibility (again, humans). With these two main metrics sorted, many decades ago, there aren't much left that could explain why people hear those differences (so claimed..), other than biases of all kinds, and of course Placebo effects and that's why our respected PhDs in the field stressed the need for DBT!!, without that, experts like Dr. Floyd Toole don't care what we think/hear.
It's all well understood science, the understanding of which by scientists/engineers, under things like coid, viruses, has not changed for decades. To save time, effort, and money, the sooner hobbyists focus on values based on features, practicality factors such as space, weight, aesthetic, and output capabilities (for amps), the better they can just focus on enjoying the music and movie sound tracks lol..