Interesting thread. One thing I rarely see is some type of pre/post measurements of the mains regarding noise, etc., despite the use of some pricey gear in a lot of cases. Meters like the Trifield or Entech are relatively inexpensive and will display some type of noise.
Anyway, my question is whether any of these devices offer any sonic improvement if the power is already pretty clean. In my case, post-treatment using a TriField EM100 meter I get readings varying from about 10-35mV on a 20 amp dedicated line (10 awg). Prior reading were 60-120 mV. Noting used on the dedicated circuit, but about 8 plug-in G-S filters at various spots in my house.