I am going to play to this very interesting problem in its toughest version, the single-source two-channel one.
It just doesn't seem like a hard call to me if the system in question has more than one source, or more than two channels. Anyway Jmcgrogan2 called it for a twin analog-digital front end, and Snofun3 did it for multichannel.
I can't see downgrading wire. Mine didn't cost enough to represent a serious cash value, and one cable is custom anyway. It would be the speakers, Nrchy. I went through a lot of upgrades with lesser speaks than the ones I have now, and I still had fun. I would downgrade them first.
I may even have to do it in real life. My spouse wants family TV in the living room and that's going to cut seriously into my listening. If it turns out to be too much, I may go with monitors in my private room.