Need Some Suggestions - Where to Start?

I have the following:

55” Samsung TV 2019 model so no eARC just ARC

20 year old Yamaha Receiver (no HDMI inputs)

5.1 JBL Speaker set - Northridge N24 bookshelfx4 and Northridge sub - also 20+ years old (budget set from Best Buy)

The speakers are mounted in the front and back on the wall but close to ceiling. The house had been wired for surround and that’s where they were placed.

I have not really messed with anything in that room as it was a playroom but now looking to improve the sound for a media room. Cost conscious, so not looking at spending $5000, but curious where I should start? I played some demo scenes on YouTube tonight and it didn’t move the needle at all (as far as sound). For starters, I think the rear speakers need to be pointed down and inward toward the coach below as right now they are pointing more straight, but not sure that is going to make that much of a difference.

So…where would you start? Receiver? Speakers (I don’t want to do front towers…would prefer mounting smaller speakers)? TV probably won’t change yet. I had even thought of just simplifying and going the Sonos Arc, sub and era300s instead of chasing it with mixing and matching, but open to suggestions.