Well, Sonos is actively working on Alexa integration (actually, integration with any voice-controlled assistant): https://www.cnet.com/news/sonos-demonstrates-amazon-alexa-co...

In the meantime, you can connect an Echo Dot to a Play:5 (or any other Sonos speaker that has a line-in): http://www.sam-mallery.com/2016/12/5-tips-for-using-amazon-e...