I have two Isotek power conditioners in my system. I like the results a lot--a little bit more openness and more natural imaging (instruments seem to be floating more freely in space). I did not hear a change that was specifically related to "noise."
I heard a demonstration of Isotek at a local dealership. The dealer had a dedicated power panel and dedicated runs off of the power panel into each room. Even with this sort of specialized room power treatment, it was fairly easy to hear a difference with the Isotek in and out of the system. The demonstration also utilized a noise meter that has numerical values as well as a speaker that plays an amplified version of the noise on the power line (typically hiss, sputtering sounds, and music from a radio broadcast). The Isotek power strip was the most impressive item because it made a big change in the meter reading of noise and improved the sound quite a bit for the relatively low cost of around $500. The models higher up the range did more, but at a much steeper price. The two conditioners I bought were on the more expensive side of the company's lineup.
