Power conditioner some say yes and some say no.

Furman. 
 Have 2 of them,  first one bought about 1991 or 92? Maybe?

still in use. They make good products.

also, we use a early 2000’s monster plug in strip, 

still rocking along.
   All components unplugged if gone for extended time. 

I use a Furman P2400IT for a few reasons.  1. The power from the wall fluctuates between 118 - 124 volts.  2. The Fruman eliminates potential ground loops, line noise, yada yada yada.  3. Protects my system against power surges.  A friend had his house struck by lightning last year.  So it could happen.  As someone once asked me, does it make sense to spend 10% or less, of what you've invested in you system, to protect it?  https://furmanpower.com/product/20a-prestige-symmetrically-balanced-power-conditioner/#  This biggest single improvement it makes is the improvment to my state on mind knowing it's there.  

In my case I have to use one -- one of those old Tice units (badly reviewed sometimes) and the big old "power block" storage device. 

I bought the set simply because my house is wired is at 30A, my power-amp if used at higher volumes caused the lights to dim and if we were also using the air conditioner and/or washing machine we'd trip the breakers. The conditioner/power storage set eliminated the problem.

I thought I heard some reduced dynamics when I first plugged them in, but I had just gotten through reading someone who said the Tice units "stangled" the sound of his system. I don't hear it now. I don't know if my initial impression was biased from his comments, I've gotten used it or what. I will say I enjoy the hell out of my system and until I move to a place with more robust wiring, I'm stuck where I am and it's not a bad place at all -- I like being able to "open it up" without fretting about the breakers.

I should add I'm kind of a 'budget' audiophile -- what I have is what I could afford.

Again, I’m agreeing with jason bourne 52. I suspect power conditioners are a cottage industry exploiting the placebo effect. Having practiced medicine for 30+ years prior to retirement, I am familiar with this effect. It is relatively easy to install a power conditioner, just plug it in. But to make a meaningful improvement in,say an amplifier’s, performance, one must disassemble the device and modify the power supply, usually by installing increased capacitance.