Furman Elite 15 PFi - how to tell if everything is working

Hello all.  I just purchaced a used Furman power conditioner. I already have a lesser set of Furmans working in my system. My sound is extremely quiet, rich and spacious already, so I'm not expecting any big improvement in the sound.  The reason I'm buying the Elite 15 PFi is because I have a lot of equipment on my 15 amp services (no way I'll ever re-wire to 20 amp).
While I don't think I'm having problems (never tripped one of the breakers), just the draw from my Magnepan 1.7i speakers on my Bryston 4bst amps can be significant at peak volumes.  I generally like my peak volumes to be in the mid to upper 80 db range. I have had a few instances where - at peak volumes or a times of load vocal chorus' only - the music might sound slightly harsh.
What interests me about the Elite 15 PFi is the extra headroom they can supply to help with instantaneous peak power requirements. I have read enough people say they hear no difference between their amp being plugged into the wall or into the Elite 15 PFi, so I figured I would give the Furman a try.
My question: If I A/B test the sound - Amp plugged into wall vs. Amp plugged into Furman, and I hear a detrimental difference in the sound, I guess I'll know the Furman is working.  But, I have read a few posts saying the Furman power factor componant of their Furman wasn't working.  What if I hear no difference between wall and Furman?  How do I know if the Furman is working? 
Any way to easily tell?

Thanks,