As someone who cares about audio fidelity a lot, there is definitely a diminishing returns. You’ll see me here telling people who complain “I have to constantly turn volume up and down for dialogue in movies”. That’s because your sound is TV speakers, basically phone speakers, go buy a sound bar and your life will get infinitely better.

If you want to go further you can get a nice set of speakers, even surround sound, and it’s fun, but it’s not as impactful as the first step.

Then though if you’re already at a sweet 7.1 surround sound system, it’s not going to matter if you get the high end cables, or spend 5k on the most bestest receiver. At that point you’re just wasting money. You may get… 1-5% better fidelity for… 500% of the cost?

I have a high-grade sound bar, and I still have to constantly turn the volume up and down. The problem isn’t the gear, it’s the mastering. Christopher Nolan went all in on that when people complained they couldn’t hear what characters were saying in his films, declaring that he will only master his movies for the cinema - home setups are too inferior. Nolan, my dude, I saw your movies in the cinema, and I still couldn’t make out a word of what people were mumbling to each other. Why even bother writing the script in the first place? Most other filmmakers aren’t much better nowadays, and I wish we can get back to the time when people who know what the fuck they’re doing are responsible for sound mastering: One master for the cinema, and another one for those watching at home.