On what I call "fine" changes to your system, in which I include power cables and power conditioners, I don't recommend A/B ing. Have a friend change (or not change) the setup while you leave the room for a while, then walk back in and see if you can recognize the change that power conditioners and cables make. In other words, do a blind test with a time lag. I say this because we audiophiles have trained our ears to hear fine changes when we're concentrating, but it's very difficult to hear fine changes when you have nothing to relate those changes to. In other words, can you actually hear the difference on a day-to-day basis?
I recently purchased a Shunyata Venom 16 with an expensive power cable. I heard the difference when I listened to the comparison of my system with the Shunyata and without. The system sounded darker and enclosed without. With the Shunyata the system was less dark and more open. Enough though that I would hear the difference if somebody pulled out the Shinyata and I turned on my system without knowing? Maybe not.
I know I would notice if my Hovland Radia amp were replaced. My non-audiophile neighbor noticed when I replaced it with a Linn amp. He didn't like the sound. I would notice if my Pass preamp were changed. And absolutely notice if my Sonus Faber Olympica Nova 5 speakers were changed to some other speaker. My power conditioner, not so much. It seems like a lot when you grit your teeth and A/B these fine changes, and I believe we audiophiles even pat ourselves on the backs for noticing differences. But on a day to day basis.... I'm not so sure.