Interesting question.
I’ve done three types of filtering. First are parallel filter chokes, Hammond 193L and 193M as suggested in a number of threads on the Audio Asylum a few years back and I believe are similar to those used in the RGPs.
The second type are ferrite clamps on power cords of appliances and other equipment that have SMPS’s in the house… microwave, washer, dryer, DVD players, TVs, all the extension cords where phone / tablet / PC power supplies or chargers are plugged in, etc.
The third are a couple types of parallel filters, a couple from Bruce Brisson’s DIY Audio Kits and several Audioprism Quietlines (I suspect the Noise Harvesters would work well here too). One of the DIY Audio Kits filters is on the same AC circuit as the P10, the others are on other circuits in the house, placed somewhat by ear… I originally used a few more than now and did not like that as much.
While the P10 made a HUGE difference in the sonics of my system and improved the sound quality above anything I had before, adding other conditioning upstream still produced significant additional improvements, especially when applied at the sources of problems (i.e. chokes on the cords of noise-producing appliances and equipment).
Still, they are secondary improvements that are not as significant as that produced by the P10.
I also tried the P10 plugged into a PS Audio Soloist and preferred it direct into the wall, which gives me greater dynamics and bass power with only a tiny increase in noise.
Sadly, I don’t have dedicated lines in this house yet… I did them in a previous house and was VERY impressed with the improvements. I suspect dedicated lines plus the P10 would be a very effective match.
Greg in Mississippi