PS Audio Stellar P3 Vs Audioquest Niagara 3000

Inserting a good preamp will most certainly help in dynamic and musical involvement (though no experience with said Mac C22).
PSA regenerators as well^, but PPP model and above. Even so, lumping front ends together with amp/s is not advisable when possible ime.. Sound can then get a tad constricted/mushy (dynamic and separation suffer) at higher volumes—even with their P20.
So, ideally two separate dedicated 20A lines plus two regenerators.
But once dialed in (with right setting of Sine/MW strength and correct application~what gets plug where etc) there’s no going back.
I understand you have ‘stable’ grid, however again ime ymmv, a variance of just 2-3V (under/over voltage) is enough to turn one pleasant session into a headache inducing one.
Long time happy PSA user here, have tried many other offerings (some much costlier) but ultimately back to PSA, as I find having stabilized voltage is one key aspect to my many great listening sessions.
Btw.I found Shunyata HC/XC series power cables to work well with PSA regens.
For signal cabling try Siltech, for your system and sound goals—I think a pretty good match.🍻

@uwikkkz Hi, yes contact/consult Mr.O..
Known him for 25yrs, bought some of my earlier stuffs off him. SF Strads, Soulution, couple of Magicos amongst others, and some nice cablings too (Kubala, Synergistic etc). Although he no longer today carries all the aforementioned brands, I just recently added a P20 through him. Good man, great service.