FURMAN, PS AUDIO, ISOTEK??

With any power conditioner that has magnetics in it (the Furman and the PS Audio both do) should not be run past 50% of their capacity, else they will degrade things rather than help. The reason is distortion of the AC power, which usually becomes pronounced once a transformer is past 50% of its capacity. This make diodes more noisy, power transformers more noisy, and likely is the reason you see variable opinions about the usefulness of power conditioning.

For the most part, we recommend that people avoid using AC conditioners with our amps. IMO, the best use of conditioners is with the front end of the system.

Now there is one power conditioner that really works and can handle a lot of power. It was made by Elgar and is not a high end audio product. But right up to full capacity it can make a perfect sine wave at its output and is the only conditioner I know of that can do that. It is mechanically noisy, so to use it, it is installed where your breaker box is and then the line that runs the audio room is connected to it. They are not cheap, and Elgar does not make them any more :(

The Furman is a good unit as long as it is not overloaded. It is used a lot where AC voltage is variable, as it will try to keep the line voltage stable (it has a circuit for switching taps on its isolation transformer).

It is most often used in studios. As I mentioned before though, you do not want to push it hard. I would not use it with a power amplifier unless its a small transistor unit.