It is not possible to play the same music to both the Echo Dot and the Sonos speakers at the same time.

Thank you very much for your quick response, then... I will just have to expand my Sonos ecosystem and that's it.

Hi ​@Garshal . One way you could add another Sonos speaker relatively cheaply would be to pick up a used Play:1 or Play:5 (gen 2). You can use your Echo Dot to add voice control to it, if that is important to you.

Just a thought.

Hello ​@John B thanks for your reply.

It's not very important to me, it was just to take advantage of a speaker that sounds relatively good and that I already have.

My idea is to create a music ecosystem throughout my home, the problem I have is that I have three floors and when I go from one to another, I stop listening to the music because I'm too far away unless I turn up the volume a lot, but then my neighbors will either come to dance with me or they'll come with the police...

As my project is medium/long term, I will gradually buy this entire ecosystem that I have in mind.

Sounds good. In every sense. That is what Sonos is for!  We have Sonos in every room now, with a total of 14 devices. I am an unashamed Sonos fanboy.

​@John B 

what would you suggest for a less expensive Sonos option to put in my daughter’s bedroom that would tie into our system? Was looking at an echo but want to be able to play music on multiple speakers so that won’t work. 
Thanks!