I did actually chase the unicorn with cabling for my main system l, and am now done with that, after testing loads of cables and driving myself and my family nuts blind AB testing many cables. It’s definitely rabbit hole that once you change one thing, it sets you down a path! Thankfully I’ve emerged from it and my system is better as a result. I now view cabling as a primary component of my system - almost as important as an amp or speakers even, that can make or break a system. I found what many others have found, that speaker cables and signal cables make the largest differences, in a few primary areas: tonal balance, transparency and speed. As you move up in grade I found them to be more revealing. Power cables I found to also impact these areas, significantly, but less so. I found that the difference moving from a middle of the range power cable to a highest end power cable adds space detail and air AROUND the vocals and tones. For me it was the difference between having your system play music vs having your system present the music in a way that seems as if the performers are in front of you in your living room. Interestingly my non-audiophile wife and daughter also noted these differences and (blindly) picked the exact same cables that I thought sounded best. My daughter said “this makes it sound like the performers are on a stage in front of us and the other one doesn’t”. The only problem is, while they clearly heard these improvements, they just didn’t care! Oh well.
Of note, in many cases more expensive cabling didn’t translate to a sound I enjoyed more. I found I didn’t care for the very pricey Audioquest speaker cables (tested Firebird biwire and I found I also didn’t care for the top end Transparent speaker wire. In some cases I found the top end of different brands to be equally good but just a different style of presentation (top power cords from Audioquest and Shunyata). And in yet other cases I found top end cords to be entirely lacking in something (Nordost Valhalla 2 power cord was very obviously missing bass energy of other cords). All verified with blind tests, and all likely results specific to my system.
Very happy I went through that process, but I’m also very glad I’m done with it now!