If you can find a pair of PLAY:5s, gen 2, sure. That would be difficult, I suspect. As long as you’re running S2, you could more easily add a pair of Sonos Fives. 

The second Sub is a judgement call. I don’t have one connected to my PLAY;5s, and don’t really notice it.

You could also move the PLAY:5s from being surrounds, and replace them with your choice of a pair of Sonos One or Sonos One SLs, or Era 100s, or even some of those IKEA speakers, and I think you’d be fine with them as surrounds. 

Thanks Bruce. That is a good idea to move the play 5’s as I anticipate I will be listening to music more in the other room then get a cheaper set for the surrounds. Just one question for clarification. Are there two different speakers with similar names play 5 and sonos 5?

Yes, kind of. Think more as evolution, with very similar form factors. The first was the PLAY:5 (which eventually got the moniker of gen 1 added), then the PLAY:5 gen 2, which was finally supplanted by the current model, the Sonos Five. 

For what it’s worth, I have a pair of the PLAY:5s gen 2 flanking my Arc, that I use strictly for music, reserving the Arc for the TV. They’re great speakers, iMHO, but aren’t sold anymore, since the Sonos Five supplanted them several years ago, in 2020. I’ve not felt the need to update them at all. 

Yes I agree. I love my Gen 2 speakers. I think the sound quality is brilliant. My play:3 is fine in my study where I am just ‘Hearing’ music in the background while I am working, but when I am actively ‘Listening’ the sound quality of the bigger speakers is awesome

I think Sonos marketing picked the confusing names just to stick it to the customer support folks that have to live with the confusion. :-)

Hard to argue with you, I love mine too. ;)

I’ve got a stereo pair of PLAY:3s in the bedroom, they’re nice too, but not quite as nice. Someday, I’ll upgrade, but since they’re working fine, it’s hard to convince myself to replace them, and I’m out of rooms to put new speakers in.

And, of course, some of us were shafted by the introduction of the Five. For example, I recently decided to pair my existing Play:5 with another one for stereo. But the newer Fives aren't compatible with the older Play:5. I bought mine in 2018 so hardly a dinosaur is it? But now it will have to be confined to the scrapheap and I'll have to buy more Sonos product if I wish to achieve my aim. Still, as long as Sonos are doing their bit for the planet what's there not to like?

I wouldn’t think it needs to go to the scrapheap. I’ve always either repurposed the  ‘older’ speakers to other rooms, or gifted them to friends and relatives. Much like old computers, phones, and other electronics that I don’t use myself. And the nice thing about Sonos is that they’ll give you a discount on a newer device, without forcing you to send the old one back, so you can get something to replace it, and still keep the old one. So far, Dell, Apple, etc haven’t caught on to that idea. 

For out of production hardware the used market has a lot of reasonably priced Sonos gear.

I’m also out of rooms, the spouse is not amused at the Gen 1 Beam that now lives in our spare bath but it was that or the garage.