If the output power were perfect from a P5 then there’d be no need for a P10 or P20
In reality nothing is perfect. There are limits to what any power conditioner can do.
One of the pain in the neck things in audio systems is high frequency noise. It can creep into any component and be “received” like a radio (think crystal radio.) What makes it hard to deal with is that it’s transmitted by parasitic capacitance across almost any component: It “rides on the top” over transformers, capacitors, inductors, resistors, even just the printed circuit board.
The best thing to do to cope with high frequency noise is to not generate it at all. Keep PC’s away from audio systems. For that matter keep cell phones, Wi-Fi, Bluetooth, light dimmers, anything with a computer … away from audio systems. Obviously we still need to live with our systems, but life gets noisier and noisier and there’s more and more crap in the power (and other cables in our audio systems) all of the time.
Power conditioners can mostly deal with low frequency noise, but they can’t really fix radiated noise and conducted high frequency noise is hard to control always.
The Noise Harvesters get rid of a little of the conducted high frequency noise. They are far from perfect (nothing could be perfect for their job), but cheaper than a lot of other things you might do to cleanup power lines and they can help a little with some of the noise that’s hard to get rid of other ways.