best power conditioners under 4k

I can hardly say what is "best," but I've owned a few brands over theyears (Furman, Shunyata, Isotek) and I am really happy with my recent purchase of Isotek pwer conditioners (Titan and EVO3 Sigma).  I bought these after hearing a demonstration by their sales representative.  The big change was between no conditioner and their relatively inexpensive powerstrip with built in conditioning.  The smaller improvement, at progressively higher price was still worth it to me, but, declining marginal utility is clearly at work here.  

Whether you need a conditioner may depend on
where you live and the effect the grid has on your line voltage. It can be unstable and/or have noise. I live in a city and the power to my house is dirty. I’ve ruled out noise from appliances and devices inside the house since my electrician rewired my service panel plus installed a subpanel with two dedicated lines.

Adding a Core Power Equi=Core 1800 (balanced power) to my system lowered the noise floor significantly and improved the music presentation in every way.

Right. But not for the reasons you think. You're still getting noise from your appliances, and everything else for that matter. All that happened was you improved that one little thing. You can do the same for every inch of wire both before and after the conditioner. Which you could have done instead of the conditioner. And let's see that thing cost $1800 that would get you, ... uh huh.... right. You could have skipped the conditioner and had even better sound with unfiltering. Way better. And that's to say nothing of the panel and lines. All because it doesn't work the way you think. Oh well....

I use Shunyata conditioners in my main system and Furutech in my other system.  Systems are dead quiet with no lack of dynamics. 

Right. But not for the reasons you think. You're still getting noise from your appliances, and everything else for that matter. All that happened was you improved that one little thing.

Improved a major issue to the noise floor. I'm living in an old rowhome in an old neighborhood with shared lines, shared transformer and ungrounded houses.

Of course, appliances are adding noise; they're wired to the panel on both legs. Tweaks could be used here, but right now I'm satisfied with the improvement.