Power Conditioners

So the German one is the Inakustik AC-3500P (which I was almost going to buy, I just had a little more money to squirrel away for it)
Then I was in contact with an Agon member, who I asked what he has, he shared and as I was already interested in the Inakustic saw the value in the Puritan.

Puritan PSM156

As for the Niagara products, I have only ever read or been told good things about them also. For me the price / performance was a best fit for my budget was the Puritan.

Audioquest Niagara 1200 is the best! Don't have to mortgage house to get one and it works! Very black back ground and the music leaps from my speakers. I hear what I hear, your results may differ....

I added a Niagara 1200 last year and experienced an immediate improvement in SQ.  Blacker background to music, individual instruments were more distinct, the slightest nuances of music became much more defined.  I'm now changing my system layout by adding a Symposium Acoustics Foundation Rack Ultra.  I'll leave the Marantz theater processor, multi-channel amp, and BD player in my present cabinet/rack and use the Niagara 1200 for those components.  I'm adding a Niagara 3000 for my main audio components going into the Foundation Rack Ultra.  For that setup all power cables are Audioquest Tornado (High-Current and Source).  
The bottom line is that I was so impressed with the outcome of the Niagara 1200 that I am taking everything to a higher level by reconfiguring the system and adding the Niagara 3000, connected to a dedicated 20 amp line, specifically for my main rig.  The Niagara products work exceptionally well.  I stand by them and can't recommend them enough.

@millercarbon knows all. He is never wrong and has the best of the best...for him, probably not for you.

@rixthetrick

Take a look at a PROPER power supply for an amplifier here:

https://www.ti.com/lit/an/snaa057c/snaa057c.pdf?ts=1601059701990&ref_url=https%253A%252F%252Fwww...

And another one:

https://elektrotanya.com/bryston_4b_sst_amplifier_schematic_sch.pdf/download.html

Everything you say you witnessed in the German power conditioner are ALREADY almost all in the power supplies of properly designed amplifiers.

Apart from extreme overvoltage protection and voltage regulation (as I said before, in this case you need to take your power company to court), there is nothing else to gain from spending on a power conditioner.