It is hard thing to A/B test. I am not about to rip out my cabling that runs in walls and drop ceilings and replace it with newer digital cables and then go back again, and even expect that an aural memory from one listen to another is reliable. I did some testing between bog standard cat 5 and the most expensive alternative at the time, by running wires directly from the router to the streamer of the day and couldn’t perceive any difference. I split the difference and bought something costing in between just in case I was wrong but I’ve been happy with the results.
I also tried a fancier router and didn’t perceive any improvement. Recently ATT changed us to fiber and again I don’t detect any difference.
YMMV. I would just comment that if your system is so fine tuned that changes in digital cables can sound very significant, then I congratulate you on the excellence of your gear