What is your experience with the law of diminishing returns ?

You guys gotta check it out. Low mass inexpensive systems are where it’s at. No more house AC, AC ground, no more speakers, speaker cables, amplifiers, preamps, interconnects, digital cables, fuses, no more transformers. No more distortion. No more noise. No more pencils, no more books, no more teacher’s dirty looks. 🧐

So there it was...

A different perspective...
Twenty years ago, when I had better ears and a less expensive audio system, I made a visit to the local high-end store. I had $5k invested in used equipment (ARC tubes, Soundlab Dynastats, HGS sub). Listened to my reference music on an $80k new system (Martin Login top of the line bi-amped with four Krell monster mono amps, etc.).

The higher end system definitely sounded a lot better. The 3D soundstage really stuck in my mind. After an hour of listening I walked out of the store with a big grin on my face thinking I didn't really hear $75k of difference.

Yeah, we can try to fool ourselves and at times we can even be successful.

Cables and power cords are components and as such they can sometimes give as much sound change as active components.
However, speakers might not be good enough, so whatever you replace in the chain give about the same magnitude of change.
Or, your system is a total mess, completely in disarray, and whatever you do it won't matter much - same mess.