How would you upgrade my entry level system?

Five grand in the context of your current system is a lot more than an upgrade and in my book calls for some serious thought.

Sounds like right now you are mostly using it for playing background music. With maybe some occasionally more dedicated listening. The point of this isn’t to see how good I am at guessing games. Its to get you thinking.

Which matters more, how great it sounds sitting in one precisely defined sweet spot? Or anywhere around the room? How likely is this to change over time? Ditto the room- will you be staying put or moving?

What are your more longer term goals? You could plow the whole five grand into a classic highly regarded speaker, one so good you could spend the next however many years building an awesome system around them and still love them. Or you might be a whole lot happier to budget the whole five grand to a whole new system.

This kind of thinking it through approach is the only way I know of getting anywhere but broke. Anything else boils down to asking a bunch of random people how they would upgrade a bunch of stuff they never would have bought in the first place. Which you just did. And got a good answer anyway.

Thanks for the responses.
Guess I have some thinking to do.
short term: try Tidal streaming. Consider non Sonus option. 
Medium term: consider upgrade on speakers and then build new system.
I like the existing sound.
would just like to more captivated, can't articulate it any better than that.

Get a pair of Tekton DI's for $3K and sell or put those Audiovectors in another room! Changing speakers will make the most difference (and improvement) over anything else! Honest!

And quit streaming, if you want to be captivated...

My thoughts:

1) System setup. Have you spent time dialing in the speaker and listening position?
2) Room Treatments- Without knowing anything about your room it is hard to suggest, but often they can make an tremendous difference. With GIK you can get their Room Kits starting at under $600, and if you send photos and measurements of your room, GIK will suggest placement (they do a lot of professional audio installations and know their stuff).  
3) Absolutely upgrade your streaming service. You can get CD quality from Deezer, Tidal, or Qobuz. Tidal offers some higher resolution streaming, but is more focused on MQA now (you can research MQA yourself, the short is it is a highly debated area of audio) and Qobuz offers hi resolution streaming.
4) With the Sonos, you can get pretty good sound out of it if you use an outboard DAC, but it is limited to 48khz, so no high res streaming. If you keep keep the Sonos, I would try a Schiit Modi Multibit or Bifrost DAC. That said, moving up to something like a Bluesound streamer with an outboard DAC is worth doing.