I tried a PSA Stellar PowerPlant 3, but eventually sold it. I actually had an entire PSA Stellar stack.
Anyway, I was looking for AC mains noise reduction, which the PP3 did not provide (as already mentioned by others here), so I let it go. What really helped me with noise reduction was a Puritan PSM156 power conditioner. I checked results with a simple EMI noise meter, and the difference using the Puritan conditioner was measurable. The Puritan also touts blocking DC, but I think you have to have quite a bit of DC present in order to notice a measurable difference.