A sub is a great addition to any Sonos HT setup - so I don’t see an issue, that’s assuming you have updated your system to the S2 App, as the sub (Gen3) is S2 compatible only.

The optical connection to the TV is really your only option with the older Playbar, but that’s absolutely fine for 5.1 Dolby Digital surround audio.

The best streaming Apps are probably Netflix, Amazon Prime, Disney+... to quickly name three that immediately spring to mind, but just check your TV supports those Apps, or can pass-through the DD 5.1 audio through its ports, if you decide to access those Apps from peripherals, such as FireTV, Apple TV HD etc.

Thank you Ken

I'm not sure where you’re situated but here in the UK a Sonos gen 3 sub is expensive Am I correct in saying that with the addition of a sub that all the low frequencies sent to the playbar and surrounds are sent to the sub and hence “freeing” the playbar and surrounds to handle the mid and higher frequencies and providing a better overall sound package.

Kind Regards

Martin

Yes I’m in the U.K. too - the sub is expensive, so you might want to check out this Sonos shopping area from time to time too... https://www.sonos.com/en-gb/shop/sub-g2-b-stock.html

(out of stock at the moment, but perhaps keep an eye out for any changes to the page)

I ‘think’ the Sub crossover is set around the 80Hz frequency level, or thereabouts, so any frequency at that level, or below, is handled by the Sub… it sounds pretty good to me but I’m using mine with the Arc.

Note you can now have two subs with a HT setup, but one of the subs must be a gen3, but if you’re just thinking of getting the one Sub, then I see no harm in the Sub gen2 (when available) at the Sonos link above, perhaps? Just none available at the moment and I think the gen3 might be on back-order anyway until mid-March - it’s quite a popular product.

I’m also in the uk. I have a Playbase and added the sub when funds became available. It’s worth doing. DD films are enhanced, and music also sounds better. 

Without a doubt if funds allow adding a sub is a big boost to movie / TH experience with a play bar. Given the choice between spending on upgrading the play bar to an Arc or adding a sub to an existing Playbar system I would get the sub first without hesitation. DD 5.1 over optical is perfectly fine and whilst Atmos is nice enough it is no substitute for Bass! The extra bottom end really fills out the booms and bangs for action movies and also has the added benefit of improving the music experience too. If you can pick up a Gen 2 refurbished or NOS then I’d say go down that route - unless you’re thinking of adding a 2nd sub to the same system there's really no benefit of the Gen 3 sub - in fact it has some subtle drawbacks in the form of ‘worse’ RF shielding (opinion only and based on owning both and comparing side by side in same room).
 

Good luck with your decision and enjoy!