Amir’s conclusion actually says “So if you have audible mains related interference that is above a few hundred Hertz, then the PSM156 may have an effect”, which is decidedly less dogmatic than my friend @samureyex. If you read Amir’s stuff on other power conditioning products, what he pretty consistently argues is that AC filtering is usually unnecessary because well-engineered products always have, and must have, power filtering built in that occurs before the conversion of AC to DC.
My take is that in your use case, you are arguing that the interaction of multiple devices has generated noise that has been dumped back into the AC mains, and that one or more of your devices has failed to filter that noise before conversion to DC. And this would be very easy to measure. Now Amir, who can get dogmatic himself at times, might argue that any gear that fails to filter out that noise is poorly engineered. I have a different view.
I have alot of tube gear, which is far more susceptible to noise than solid state, particularly when you’ve got the low level signal involved with an analog front end. I’ve had annoying noise gremlins that required a fair amount of experimenting to eliminate. In one case, I ended up actually having to remove a filtering device that was somehow adding noise, and replacing it with a simple star-grounded power strip. During my experiments, I came up with a crude but effective way of measuring my results: I used a db sound meter app on my phone and held the phone next to the speaker while turning up volume to 12:00. My control sample was my digital front end, which even with all my tubes was very quiet. I then would do the same when I engaged my tube phono pre into the system, trying all my different power combinations. As I said, crude, but highly effective (for me anyway). YMMV.
