Headphones

Your setup is fine, better than what 95% of people have.

As far as where to listen to music, literally any streaming service. (Free) YouTube has some pretty noticeable compression on everything but the differences between Spotify, Tidal, Qobuz, Amazon, whatever other platform are so minute that you will never hear them unless you are meticulously A/B testing them together, and even then a lot of that could be placebo.

I personally went with Tidal back when I was chasing audio fidelity a year and a half or so ago and I ditched Spotify for it since they're the same price (I'm on Tidal's HiFi tier, not the Max one) and I wanted to reset my discovery algorithm. Spotify was recommending me the same albums for years on end even when my tastes were broadening out past just prog metal, so I wanted to reset. I also didn't want podcasts clogging up my feed because I use a separate app for that. In general Tidal and Spotify are 90% similar to each other, with Spotify having more social features (which I don't care about at all) and Tidal having more in terms of information about the artists, which is pretty cool. Tidal's a little buggier but it rarely has an impact that lasts more than, say, 10 seconds. I don't think you can truly go wrong with any of the big streaming platforms though, so do whatever your budget allows.