If you are using a combination modem/router my one remaining suggestion is to use a gas discharge surge suppressor at the entrance of the cable to your building.
I use a lot of things which are Ethernet connected, and a surge coming in from outside via the cable modem could take a lot of things out. OTOH, if you are 100% Wifi, then the only risk is to your router.
I don’t think there’s a realistic router upgrade from what you own. The best you can do is perhaps use a PC/laptop or phone WIFI analyzer to make sure your router is on otherwise unused channels. Even a strong Wifi signal can suffer from noisy neighbors, and the analyzers are free.
New routers and receivers may have faster transmit speeds, but music streaming is lightweight. It’s not going to make anything sound better if you improve your download speeds by a factor of 100, but putting your router on unused channels will. I think newer routers do a better job. 6 years ago they all seemed to cluster on the same 2 channels, causing a real headache for apartment dwellers.