after my system and hearing developed
Close. Not hearing. Your hearing didn’t change. This is a common mistake people make, hearing. Hearing is passive. You hear the test tone, or you don’t. Listening is active. Listening is a skill. What developed is your listening skills, your active ability to discern details and relationships among a longer list of sonic attributes.
In the beginning you couldn’t hear power cords. Now you can. But not because your system is better. Take your power cord to a friend with much worse stuff. Swap it out. You will hear it. This will prove 2 things: one- it is not the system! You will find you can hear the difference just fine no matter what system you put it in. And two- there is no such thing as component matching! The power cord sounds just the same, makes the same difference, no matter where you take it.
This is the beginning of audio wisdom. Enjoy the ride!