What should i upgrade to?

Unfortunately for us in the public (and the best for Sonos and its investors), the ‘best’ Sonos is always the most expensive. For the Atmos TV, I’d suggest the Arc Ultra, one (or two) Subs, and Era 300s.

For ‘stereo’, I’d recommend a pair of Sonos Fives with a sub…unless you listen to a lot of Atmos geared music, in which case I’d recommend a pair of Sonos era 300s, with a sub. 

Not sure why refurbished isn’t an option, I’d think they’d be a sale just like anything else. 

If you want “the best” you need Ultra and Era 300’s as rears. And a Sub or two, of course. 

You state: “Since my TV supports eARC, I feel like I'm not getting the most out of my audio with the Beam Gen 1. I mainly watch Netflix, YouTube, and Disney+."

You know eARC isnt the deciding factor here? It is not needed for any of the streaming services you name. They all use a compressed audio stream, that will even pass a normal HDMI-ARC connection. You only really need eARC when you use a BD-player or Aplle TV that supply uncompressed streams.

If you would want to get Atmos audio you'd need a Beam (Gen 2) at least. To get the most out of your audio see ​@nik9669a 's post.

I'd skip the Beam, an original Arc would be a good price and add a lot to your sound.

For stereo music a set of Play 5 -- gen 2 -- is going to be tempting. Fives would be better but at a higher cost.

Adding a Sub to the stereo Pair you have now would also show a nice improvement. You could move your current Sub to audition that.