There are some things that just don't need to be tested. Here is an analogy to the power cord, distribution, outlet senario. You are in a small submarine well below the surface waves (power supply ripple) whose particle's vertical movement is in a circular fashion and extends something like two times the height of the waves. Large seaguls are landing and taking off from the surface creating little waves. My contention is that in the submarine you will not feel the effect of the birds activity.
What make these products even more ridiculous is that they don't do anything to the line anyway (they don't stop the seaguls from landing). I read an ad for one of the ac line conditioners that bragged about not having any coils, filters, transformers or capacitor to spoil the quality of the sound. Of course there is no sound on the power supply side. And the very things that would clean up the ac line are the things they brag about not having.
You could by a ferroresonant transformer. They actually do clean up and stabalize the AC power. They provide constant voltage and tremendous surge protection. They won't make things sound better but they will protect your valuable equipment. Problem is that they make a lot of mechanical noise due to magnetostriction (the transformer laminations actually grow and shrink as the the magnetic field varies). If you could sound proof one in a box it would be a useful addition to your system.