The isolator and upgraded power supply are two separate but additive links in the chain. An isolator or purifier will reduce the noise in the AC to your power supply (and typically other components, too); the improved power supply will allow for greater reserves of that cleaner power for delivery to your component without adding much noise of its own. If I were you, I'd start with the improved power supply. I've never met a component that hasn't improved with a bigger, better power supply--even turntables, weirdly enough. Isolators or purifiers can be hit or miss, dependent on the design and the component plugged into it.
Power isolator versus need for a better Power supply
I have a transparent power isolator, and a component with a Wall wart power supply.
If I plug the wall wart into the power isolator, does this precluding need to replace the wall wart for a better Power supply (ie. Ifi, etc). Doesn’t Power isolator clean things up before electricity arrives at the Wall wart?
I asked this question and didn't get a very good answer from the dealer that would be selling me a Power supply to replace the wall wart assuming I need to do it