I loaned my PSaudio PP10 to a friend with who has modded and tuned his system amost to perfection. It is a low power tube system and the amp has an awesome power supply. He has had the PP10 a week and isn't sure he likes it. Very similar to what you report.
Our theory is that he has tuned his system to perform best with the power supplied to the outlet and would have to retune it to the clean power. This is just a theory.
I'll be getting it back and putting it back into my system critically. When I first installed it I made a lot of mods at once. It will be interesting to put it back in and listening critcially. I must say that I am not finding my system at all deficient without it. I believe it does indeed make the clean power that it claims and provides plenty of power to the amp. There is no loss of dynamics of bass. I'll try to better understnd the differences.
The PP10 is an 80 lb rectifier/inverter system with tremendous power capabilities. I beieve the Niagara is similar. I am always skeptical of the passive cleaner devices like the one recommended above.
The PP10 also has an oscilloscope built in and analyses the power coming in. Contrary to popular opinion, power does not get cleaner at night. (my theory is that systems sound beter at night because there is less ambient noise and the listener is more relaxed).
Jerry