Play:1, Sonos One, and Sonos One SL are very similar in sound quality and quite well suited for surround duty. Play:1 is a great choice, since it’s what you already have, and you aren’t paying for features you won’t use with surround speakers.
I have Play 1s on one system and One SLs on another, can’t tell the difference but then my ears are not great anymore.
I have Ones but started to buy the One SLs because I do not use voice commands. In the whole Sonos range of speakers I consider them the best price/quality products. If you are tight on budget, you might also consider the Symfonisk sold by IKEA. They sound also good but I perceive a slightly less clarity than the One SLs.
The Play:1s are fine. Surrounds aren’t doing much heavy lifting as far as sound is concerned.
I changed my surrounds from the ones to Symfonisk and I’m sure the Symfonisk sound better when used as surrounds and my ones did.
the ones are now used for stereo sound in the dinning room.