What makes the biggest difference in sound quality?

I'm with AC and room as foundation. Of choice Ted gave, power cable>speaker cable>digital/IC> fuse

The first five things are the room.  Everything else you listed comes after that.

Let me clarify a little.  There are people who train themselves to hear past the room and only hear the equipment.  That's an amazing feat of ear/brain effort.  For everyone else, the room is the biggest thing, then speakers, then amp, then whatever.

What a funny post @nickatnoon61.

Thanks for that.

i am considering changing my handle to 'killedacowjustnow' 😂😂

Speaking of speakers 😏, I think there is one aspect of speakers that is quite often overlooked and that is decoupling them from the floor. If they are isolated they won't transmit vibrations through the floor and color the sound. It worked for me.