I agree with MillerCarbon more often and rarely with of the naysayers.
I use PPT products but found that too many Omega Mats over isolation power transformers, rear of speakers and power boxes can result in a loss of air/ambiance/highs and too much mid-range emphasis. I also found out from the manufacturer after having found my system sounding weird was that PPT products should not be used where there are magnets. By adding and subtracting the number and type of Mats I was able to fine tune their use and benfit. I now use 2 Omega+Mats on power boxes, 2 on top and 2 beneath my isolation power transformer and 1 on the rear of my speakers at the crossover section. My friend who introduced me to them has no magnets in his system and installed all the PPT products 10X to 20X what I have now. It works for his system.
I also use SR HFT system with 32 placed as indicated in the instructions for Levels 1 through 5 and speaker kit. I tried altering some of their order and resulted in worse sound. The only one that does not work is the HFX on the tweeters (emphasizes the highs/frequency range out of balance). Neither the PPTs nor the SR products give me adequate scientific reasoning for their successful use but that doesn't stop me.
I tried over a dozen types of footers for my equipment and ended up with various Stillpoints. Those have a stronger scientific basis than SR and PPT products.