Hi and welcome to the forum.  :)

A couple of basic points:

• You don’t say how big the games room is but personally I would try 2 devices set-up as a stereo pair first.  If you use a Sonos One and a Sonos One SL paired together, you won’t need a separate Alexa Device - When in a stereo pair, the mic is disabled on the right hand device, so don’t bother buying 2 Sonos Ones..  Although Sonos don’t support all of the functionality available in an Amazon Echo device, some users prefer to use an Echo device to control their Sonos system.;
• If you do go for four devices, I’d still recommend them to be set-up as two stereo pairs.  These will be set-up as two Sonos ‘Rooms’ but can be grouped together to output the same audio in sync.
• Your last statement is almost correct: Your can use Alexa via voice control to instruct your Sonos devices to stream music from Spotify.  But please note, you can’t output the same music across Sonos and Amazon devices in sync.
• Please refer to this support article on how to set-up Alexa Groups so that devices are grouped together if you do decide to get 4 devices. Alexa Smart Home Device Groups and Sonos | Sonos

Let us know if you have any other questions.

Edit:

Added link this time!

Thanks, appreciate the response. In regards to your points…

• The games room is approx 8.5m x 4.6m, but it has a pitched roof so quite a lot of ceiling height towards the middle. I’ll need to get the electrician to mount power sockets in the upper corners of the room where I plan on installing the speakers on mounts, so I’d prefer to decide on the number of speakers before commencing works. Given the size, do you think two or four speakers would be best if I’m striving to achieve fairly even sound throughout?

• If I were to go for two speakers as a stereo pair then I imagine I should mount them at opposite ends of the long wall of the room?

• I think my preference is for an Echo device to control the Sonos system due to a combination of familiarity and not losing any Alexa features - it would be useful for my wife to be able to drop in on the room to speak to me when I’m in there which I understand isn’t possible via Alexa on Sonos?

• If I were to go for four devices set up as two stereo pairs, what would be the best configuration? A stereo pair on each short wall, or a stereo pair on each long wall? I imagine that I’d want to keep the L and R channels opposite each other?

• I’m aware that I can’t play music via the Sonos and Echo devices at the same time, but given that I’d likely be going for one of the Echo Show devices so I can view the Ring Doorbell this is no great loss given the sound quality.

• Thanks for the article, I’ll bookmark the link.

Many thanks for your thoughts, much appreciated.

For that size room, I would either go with 4 Sonos Ones, or two Fives.  If there’s a specific listen area, then Fives would be better.  If you expect people to be in several locations in the room, not surprising for a game room, then 4 Ones may be the the better choice.

No, they would be left and right channels and general speaking the left, right, and  main listening area should make a triangle.  Essentially, like a stage at a concert.

If you go with the 4 speakers in corners though, I would still setup 2 pairs, but change the setting for mono.  Or try mono vs stereo and see which sounds the best.

This is what  I do in  a few different rooms.  It’s not so much Alexa features as it is having the mic/speaker of the echo near me, not across the room where I want music to come from.  Given that, if you get Ones, you could get One SLs.  However, Sonos is rumored to come out with thier own voice assistant.

Stereo pair on the short wall.  Again, mono may be the way to go, but I imagine you will want to control volume this way.  And if if you go stereo it will make more sense..  Oh, and I would alternate, so it’s L-R-L-R as you circle around the room.  Not L-L-R-R.

Thanks again for the input, very much appreciated.