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.🍻

Bvdiman, thanks so much for your detailed explanation. Much appreciated. I noticed that you are a fellow Indonesian audiophile, awesome! 
I just bought C22 from Victoria Audio M2 Mall yesterday, Lukito the owner suggested me to get the pre amp first and he was right. The improvements are a lot, better separation, MUCH better staging, a lot more details and off course authority. Even my wife who thinks Bose sounds good can really tell the difference. But off course, it became even more obvious that some constraints I am still hearing are needing proper power feed for any improvement. 
I finally found the distributor for PSA product after emailing PSA USA. I will keep in touch with Ongky from Audio Image unless you know other? What you told me about separate regenerator/conditioners make a lot of sense. Especially after I booked another pair of MC75 from Victoria Audio for bi amping. What would you recommend? A pair of Stellar 3 or a pair of P12? A pair of P20 is definitely out of my budget right now as I just bought everything within this month and I don’t think my system is high end/hi power enough to warrant a P20. 
Thanks a lot! 

It might be worthwhile to change the wall outlet to Furutech GTX-D (R) NCF before going with power conditioners.

@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.