Jada Jones and Maria Diaz/ZDNET Follow ZDNET:  Add us as a preferred source  on Google. Sonos has cemented itself as the king of multi-room audio, but more and more companies are joining in on the trend, some offering features that Sonos doesn't.  Also: Forget the soundbar: How I upgraded my TV audio with spare Bluetooth speakers Bose recently joined in on the fun, unveiling its Lifestyle Ultra Speaker, which operates in a way that's familiar to Sonos's smart speakers. Both companies offer separately sold smart speakers that can stand on their own around the house, group together for left/right audio, or pair with a compatible soundbar to perform as rear speakers. Yet, aside from a hard-to-miss $130 price difference, there are other differences to consider regarding ecosystem integration, smart features, and voice assistants. Let's break them down.…