Power isolator versus need for a better Power supply

it’s difficult to generalize about this, since some wall warts are not that bad. but generally the wall wart is a cheap SMPS (switch mode power supply) and the source of lots of noise. and we don’t know the specifics of what gear and which particular wall wart. did this wall wart come with the gear? might be ok. or the combo of the wall wort and the power isolator might happen to sound fine. these things are not always predictable. you do need to listen.

if you can find a linear power supply that can replace the wall wart that would be step 1. then step 2 might be adding the Power Isolator. alternatives might be a better wall duplex outlet as those are also sources of noise, or maybe a dedicated circuit? both those things likely would improve the performance of the transparent power isolator.

fundamentally when looking at A/C power grid questions; you look at it from your home power source outward, look at power grid noise sources in your home, and see how you can isolate as much of that from your system power grid. but now i’m moving away from your actual question.

Cheap wall warts could push noise both back into the "clean" side of the power isolator and provide less than ideal power upstream.

Will a better support like an iFi help your sound quality?  I don't know, really, but I do encourage people to keep dirty power supplies outside of the clean side of a power conditioner.

If I plug the wall wart into the power isolator, does this precluding need to replace the wall wart for a better Power supply

Short answer, no. In addition to reducing noise a better power supply will usually improve the performance of the component over a wall wart.  An analogy might be an athlete eating a diet of healthy food versus loading up at McDonalds — one of them enhances performance, the other not so much.