The Puritan PSM 136 & 156 present the best value in power conditioning. However, do not audition a Shunyata Everest or Denali-Typhon T2 combo. I had a PSM 136 and upgraded to the Denali-Typhon combo. It's easily an improvement equal to a $25K component upgrade. A used Denali can be had for $4K.
I'm not trying to hijack the post with a recommendation, but I was in the same situation thinking of upgrading to the PSM 156, which is stellar. But, I can easily state that the Shunyata performance elevation to my system was jaw-dropping. No other component, speaker, or cable (even the AQ Dragon) significantly improved my system as to what the Shunyata did.