Group them together and then ask any Alexa equipped device to play to one of them and they all will play.  You can also set them up as an Alexa group and all will play, regardless if they are grouped beforehand.  The Alexa equipped device can be an Echo, a Dot,  a Sonos One or any other device with Alexa.

so which one would you buy buddy?

the new sonos 1 with built in Alexa or a new sonos one with it built in?

thank you

Either will work. If you have space for another Sonos device, then personally I'd go for a Sonos One. Just one other comment, you can only create a Stereo Pair with a Sonos One with either another Sonos One or Sonos One SL but not an old Play:1. 

This is very much a personal opinion, but I would advise getting at least a couple of Echo Dots, rather than another Sonos speaker (unless you really need another speaker).  If you only have one voice controlled speaker then you have to get in voice range of that speaker to give commands.  I don’t know anything about the layout of your home, but will that be practical?

Given that you will not be listening to music on the Dot, you could possibly ick up some some second or third generation Dots very cheaply.

I find it useful that I can position my Dots where they can best hear me, which is not necessarily where the speaker is.  It isn’t as neat a solution though; it’s another device littering the place and occupies another electrical socket.

As John B says… get some Echo Dots, they are much better for for voice than relying on the deaf mic built into the Sonos speaker. Seriously the Dots are much more sensitive and can understand you better.