A Sonos TV Home Theatre (HT) product cannot be ‘bonded’ with just one speaker for TV surround audio, it requires two, for a 5.0 surround sound setup etc; that’s if you are looking for that option.
 

I will assume you have a Sonos Play: 5 (gen2) as the Play:5 (gen1) cannot be used in a bonded HT setup, nor can it work in an S2 system, which the Arc definitely requires.
 

A single Play:5 (gen2) can be ‘grouped’ with a HT product and that is great for music playback, but you will likely find lip-sync or delay/echo issues if trying to play TV audio to the group. 
 

If you did not have any existing Sonos devices, I would probably suggest a Beam and two Sonos One SL’s for your size room, but you might now find it easier to go with a Sonos Beam and add another Sonos Play:5 (gen2) and ‘bond’ all three together and create a HT and Music setup

Thanks for the reply! 

I am not looking to gain true home theater sound in this room. 

The beam is obviously the least desirable of the sound bars, as it in my opinion lacks the punch of the others. 

But currently the Beam is $299 and my hope was to add the Play 5 gen2 to the Beam to add a bit of base, considering I already have the Play5.  Otherwise the Arc will set me back $799 for an occasional sports viewing room.

I should have been more clear, in my original post.

Thoughts?

Thanks!!

Yes, the Beam is a steal at that price and I think it should be fine in a 12’ x 12’ sized room. I have two Beams myself (Bedroom & Dining Room) and they sound absolutely fine, but each do have two Sonos Ones as surrounds.
 

I also have the Arc in a 22’ x 15’ Living Room with sub and two Fives, but it’s a bit of an overkill even for that size room. (Only the neighbours care about that though ).
 

But ... I’m getting from your posts that ‘really’ you would like the Arc - it really is upto you.
 

I love both the Beam ...and the Arc is great too... like I say the Beam is currently good value and I think you will not be disappointed with its performance in that size room.
 

If you’re like me however, you will always wish you had gone with the Arc. ‍♂️

For sure,  I currently have a Playbase and Playbar in other rooms.  Would love to have the Arc, but $800 vs $300 on the Beam, just seems overkill for an "occasional room".

Can you pair the Beam with a single Play5?  If so, I understand it will not be true surround sound.  Just hoping it can and will provide the bass that the Beam lacks.

Thanks again for your help!

You can ‘group’ the Beam and Play:5 - for music playback that’s absolutely fine,  but you will experience an audio delay/echo for any TV audio out.
 

You cannot stereo ‘pair’ the two products, nor ‘bond’ them together for ‘timely’ TV audio…. there are workarounds for TV playback during grouping. There are ‘software’ tools/options in the Beams ‘Room’ settings in the Sonos App to make adjustments to the audio out - one is called ‘TV Dialog Sync’ and that can be used for some types of TV audio to eliminate any delay/echo in a grouped room situation.

Just to add to what Ken is saying, you aren’t going to add more bass to the room by  putting in a pair of fifes, or any speaker pair really, as surround sound speakers.  They are not there for bass, that’s what subs are for.

One other suggestion, you could move your playbar to the occasional room and put the Arc under the TV vacated by the playbar, so it gets more use.