A very interesting topic.
No question "clean" power, however that might be defined, is absolutely fundamental to good sound reproduction. "Good" measurements don't guarantee good sound. My experience is that power conditioning can make a massive difference both in poorly and well designed systems.
There are several issues. Everyone's speakers, amplifiers, preamplifiers, sources, cables, home electric infrastructure, utility service, etc. differs. People's hearing and listening envoronments are different. There is also the ever changing atmosphere music is transmitted through. And the noise of your domestic appliances, mobile phone, LED lamps, switching power supplies. And those if your neighbors. And the data being sent via the grid.
And there are elements relating to electicity and sound that engineers are still struggling with. And so on.
So finding the right solutions for your situation is a painful task. To be clear, most audio equipment employs some rudimentary filtering schemes but this is not enough. Some external power conditioners might help with some people's situations. Some desiring might help others. A one page review of a power conditioner is not too helpful unfortunately.
My electricity journy started as I noticed that my system sounded much better at night, in the winters. A few very cold days with sleet the sound of the system somehow stepped up several notches. I confirmed these odd experiences (including the sleet days) with a few local guys in real time so the sample and evidence is terrible but convincing enough for me.
***My goal was to remove the seasonal-daily-hourly fluctuations in electricity and get as close to the sound of those once a year sleet days (not all sleet days were good) as possible. In summary, I wanted "good electricity" days all the time. To be clear, the sound once a year was so good that there was nothing else to ask for from the system. Just euphoria.
My solution, which was not perfect but was well worth the effort, was to replace the fuse box, rewire dedicated lines to my listening room and acquire a relatively popular AV electricity filter in the listening room. That was for a home system which ran tube amps sometimes and solid state gear sometimes. Still fluctuated with season-time-weather but overall the improvement was significant. Just much more musical.
The following guy found his electricity solution. Unfortunately it is not a product you can just pick up at the store but rather a long process. Read the thread - if you really want to improve your listening experience this can put you in the right mindset.
One caveat is that my experience is with full frequency hi-fi, including solid state and 3w tube amps, and that I am a newbie with headphones. I don't know if that matters and I don't know if anyone could provide a convincing argument why it would. There are just too many uncertainties today's technology has not resolved.