Why not both, power (distributor and cables) and room treatments. And honestly implementing room treatment is relatively inexpensive in the grand scheme of things.It just needs a lot of work. For me, I gotten everything I could possibly need, goods and advice, from GIK Acoustics. And of course, speaker placement, toe in, distance from listening position, etc. which are of course …. Free. Just some work.
From my own experience with real people, those who proclaim power cords and conditioners make zero difference, and room is all that matters, typically have zero room treatments in their rooms. They just love to bash cables. As they say, don’t pay attention to the preaching of a naked priest. Or something like that.
“Why not both,” is because the power cord and conditioner cannot fix a room, nor fix placement.
One cannot change the physics of the room interaction with a high $ cable.
Secondly, it is better to do the things have have a greater impact first, as well as the things that do not require a trip to the store.
Cleaning corrosion off the RCA/XLR and speaker connectors… and making sure that outlets connections are tight are some of the things that can make a difference. But moving a speaker almost always has a huge impact. And it can take hours or days of futzing around.
Once all that is done, I stop… But I am more of a cable denier so there is that. But a believer should probably start their cable search when the system is “as right as it can be.” And not start with cables and power conditioners as a strategy to fix and room and speaker placement issues.