Kef LS50 Wireless - optimal configuration

 Hi there, 

I'm new to this forum, but I don't think this question has been answered before. 

My current set up is Sonos Connect + KEF LS50 Wireless + Kef Kube 10b. I'm using an optical cable to connect the Connect to the speakers. I stream through Spotify (Premium).

I love the set up, it's simple and works well for me. I'm wondering though, is the Sonos Connect holding back the system? Is there a straight forward upgrade that I'm missing out on or is this the best that this system can do? 

I've read that some people are adding external DACs and using the RCA inputs, that's off the table for me. 

I'd love the input and guidance.

Thank you