Power conditioner some say yes and some say no.

There is an excellent recent article on this by John Atkinson in Stereophile; you know, the guy that does all the measurements. It’s worth the read. Of course, there are many other articles on this, as well.

From what I’ve read, there are many factors that affect "line hash" and other power issues. Generally speaking, you are much more likely to have measurable "line hash" if you live in a larger city, as opposed to a burb or more rural area with good or reasonably good electricity delivery infrastructure. The age and/or quality of the wiring in your home is an important factor, as well.

I’ve been using a Monster power conditioner for many years. I honestly can’t recall hearing a difference when I started using it with the system I had way back then. If there was one, it was likely very subtle, which is why I have no clear recollection of this. Usually, when something blows me away, like speakers or a component I heard even 50 years ago, I remember that component, its model number, the shop or place I was in at the time and who I was with. So, I’m relatively certain whatever difference there was with the Monster was subtle, at best. At this point, I wouldn’t dream of leaving it out of my chain because of the protection it provides to my components. Best way to arrive at your own conclusion on this is to try it. Worst that can happen is you take it back for a refund.

Best to just try it for yourself. Sell if it doesn't do the deed.

Some forum advice just increases nervosa. You already have experienced there is a camp with and without.

Tube gear are the only components I seem to gain much improvement on when using power conditioners.  While conditioners can greatly reduce the noise floor, particularly with SET amps, they often negatively impact the dynamics and soundstage from my experience.  I have had recent success using isolation transformers (eg. Equi=Core), which I find reduces the noise floor without negatively affecting the dynamics.  These products are a relative bargain in my view compared to other products.  I'm a huge fan now.

Why are you out $4000?

I have never found any power conditioner to be wondrous. The ones I have used - and they ALL claim not to harm the signal - are as deleterious as beneficial. I don't find the idea of a whole system conditioner too appealing. I have found upgraded individual power supplies for each component to be highly efficacious. YMMV 

Consider; the thousands put into a conditioner could be put to work in, say, better speakers, and no one can tell you whether you would prefer that to the highly conditioned, lesser speakers. ONLY a direct comparison would tell. All manner of unsupported claims are made, with very little sensibility and real world experience applied to the claims. :(