Question about the potency of various QRT type devices.

I currently own a couple of classic QRT Symphony Pro units as well as an Audio Magic power conditioner (an Eclipse II) which has a QRT module in it and they all have a positive effect on both audio and video for me.I'd like to further enhance this effect but was wondering about the relative power of various units. I realize most wouldn't be able to compare more than two different units, but any experience with any of these is welcome, as it's difficult to find any talk of any experience with some of these units.

-Audio Magic's P.E.A. units, more importantly the large unit and the now retired Monolith as they are the most powerful units (at least not in one of their newer conditioners).

-Telos Audio Design's Q.N.R. (Quantum Noise Reducer).
-Add-Powr's Symphony Pro units (which are supposed to be more potent than the old QRT Symphony pro units, but I don't know how much more potent). I know their Wizard and Sorcer units are more potent than the Pros, but they are also 2.5-5+ times more expensive.

-Nordost's Qx4 (being their most powerful QRT standalone unit).
-The QRT module in a Walker Velocitor (I realize the Velocitor has had five different iterations so I'll relegate this to older iterations as a V is around $4,000 and I've seen earlier iterations go for under $2K).
-And I don't know if they operate on the same purported "spintronics" harmonizer principal but if they do- the Kemp P16 and P40 units.
I know HiFi Tuning and Reimyo have also made conditioners with QRT modules (as well as others listed here making more expensive conditioner units), but I'm trying to limit this to units that can be had for under $2000 used or new (based on availability).
Thank you.