Well, short answer would be to ask:
Were you happy with how everything sounded?
If yes, then start by getting it all back out and set up properly. Re-familiarize yourself with your AVR and its capabilities.
Even without suggesting a complete budget blow-out
, there are definitely things to consider.
Is your AVR good for at least 4K UHD HDR? At least HDMI 2.0? (Not a big deal if not, but those are minor items that would weigh on upgrading sooner than later.)
Some people love Pol Speakers. There are better out there... again, not a ding on what you have, but only you can decide if the SQ is good for you or not.
The Sub... This is a definite short-lister for the upgrade train. Doing so is largely based on the open room volume of where it will be placed, and what space you have available. There are a lot of very good quality budget-friendly subs available that we can turn you on to.