I have two P20’s on Monoblocks as well. mine hum loudly as well. I just had a catastrophic P20 Failure! It locked up at 193 volts! The P20 survived and luckily all the stereo components did. however a $7,900 TV display was killed. Luckily it is under warranty in home service. Otherwise is PS Audio going to pay for these mishaps? My second Ds Senior is dead. I have lost faith in PS Audio unfortunately as good folks as I think they are. The Eaton is if one thing, highly unlikely to fail. NASA and the DOJ,CIA use them! They are on life support in hospitals too. I would say they are held to a pretty high standard. Plus my upstairs system which is by no means any slouch actually sounds better on the 9PX than the P20 or Shunyata Hydra for that matter! Yes, get a P20 and be done with it. Be done with with all of your equipment perhaps! I simply cannot stand for this anymore. Being nice folks with good customer service only goes so far. I feel the products are like more in Beta stage when released to the public here. The Eaton is proven in the most critical applications the world over. Do you know how many 9PX are deployed in the world compared to P20’s? Proven, period. How it sounds is up to you but I feel it actually sounds better. Now there is a company that has put a P9x in a fanless housing for “Audiophile” use for $18,000! go figure. Considering what you can buy them for on Ebay…… I suggest get a new unit though. Since if the battery is dead it will probably cost as much as you paid for the unit if not more. You can buy batteries very cheap too if you are able to wire it together. It is very easy but absolutely do not mess it up! it can and will kill you if you miswire it! I say, what do you have to lose here? not much. A few hundred Vs. Ten Grand. Plus I as many others can attest that Ten Grand might very well be better spent elsewhere. Especially with these types of shenanigan’s.