Yes, and yes.

Thanks @jgatie.   So a gen 1 would have no compatibility issues in the mix, or with the latest app?

A gen 1 will only run S1.  You would not be able to add it to an S2 system, you’d need a newer PLAY:5 gen 2 or a Sonos Five. 

And it’s not clear which you’re running, all the speakers you listed could run either S1 or S2 :)

Thanks for clarifying, @Airgetlam. We’re running S2 :-)

I’ve got a pair of PLAY:5 gen 2 s that are running S2, they’d be ideal for that line in you’re looking for. The S1 only PLAY:5 gen 1 would not. 

Another thing you might think of doing….

Many people feel that Play:5s are more than needed as surround speakers, perhaps even a bit wasted.  You might consider adding two One SLs instead, and use the P:5s as a stereo pair for music.  A stereo pair of Play:5s sounds fantastic.  That would give you two lines in!

Unless you are listening to music in Full Mode the Fives are really being underused!

For serious music listening I think you’d find a properly positioned pair of Fives would give you a lot better stereo imaging than the Playbar. You could always group them too.

Thanks for your help, folks. After a bit more searching I’ve actually now found a great price online for a new Port, which makes it not that much more expensive than a secondhand Play:5.  We don’t really require another speaker (not a huge amount of space), so the Port seems like a cleaner, simpler, more compact solution…