I have had dedicated power to my stereo system since 1989. Every house I have bought since I have taken the trouble to run a dedicated line to my stereo but I didn’t add a dedicated line to my current house until I retired a couple of years ago since it was the most difficult to do of all of my houses. It is worth the trouble. First of all, a dedicated breaker and power line reduces voltage sag- ie, drops in voltage as the line is loaded down. I consider a stable voltage source a big deal for good sound. Second, it reduces but does not eliminate electrical noise from other sources inside the house. There is no single silver bullet that fixes all electrical noise for a stereo system. Each step taken removes a small amount of noise and grunge that affects S/N as in background noise, improves clarity and makes the highs sound sweeter. It nearly killed me to spend what I did on a power conditioner but it works. It adds to the improved clarity and sweeter highs. And then power cords do even more to reduce background noise and improve on the highs as well as bring out more detail. I have said it before, buying expensive power cords takes a lot of grit and determination. They aren’t sexy. They are nothing to look at but if you want the best sound out of your components that you can get then they are necessary. And much to my disappointment, good power cords matter after the power conditioner.
I have what I consider a hifi set up just because I have all the right names. And well, it does sound killer….