AB testing-can of worms
Power cables-can of worms

If you start off from will a perfect supply (constant voltage, perfect sine wave) improve the sound (performance) of the electronics (I think yes) and work backwards, see where you get.

I can't help but think that spikes and variations in voltages are sub optimal. I think it was someone here who said- undo your mains plug sockets (powered off) and look at the black marks on the plug connectors, evidence of shorting. That can be good.

Ears always have it.