If you’re bored and you feel the need to shout at your monitor > How much for a mains power cable?
Improving the quality of the electrical supply can enhance top end audio.
However we’re talking incremental gains and more importantly, you’d want to upgrade the whole electrical circuit path and supply, not just the final metre or so from the wall.
No doubt absolute purists do do such things but it’s the law of diminishing returns.
Periodically unplugging and cleaning RCA jacks can make a difference to the sound. I did notice a subtle change when I last did this as an experiment but that was something like 15 years ago. – As you can probably tell, I’m really not that fussed about such things.