The Sub Gen 2 and Gen 3 are basically the same. The Gen 3 has updated internals and a different Join button but sounds the same as the Gen 2. The main benefit of the Gen 3 is you can have a dual Sub setup.

I doubt I'd get a second sub, This one is more than loud enough, and also I have it next to the tv in front of me, so no need to upgrade to gen 3? It'd be a waste of money for now I think, one sub is more than loud enough it's the loudest sub I heard since my z5500 days

Yes, the Sub gen2 & gen3 are pretty much the same for HT. I would personally say to perhaps just add a Sub gen3 if you ever decide to upgrade and have the Sonos Arc with dual Subs in your HT setup instead, or perhaps if you plan to use the Sub (gen2) elsewhere in the Home… Dining Room etc.

I have upgraded my Arc HT setup to use two Era 300’s and I think they sound great as rear surrounds. So that’s well worth doing and then use the Play:1’s elsewhere in the Home too. The Era 300s obviously don’t work with your old PlayBar, of course.

During my own upgrade path, I got rid of the Sonos Boost and switched to run all on a WiFi-6 mesh setup instead, but that’s entirely a matter you, but I’m finding that things are both quicker to operate and it has improved the local network reliability. 

Well I have a single Asus ax88upro In a 2 bedroom apartment, I can use the play 1s in the bedroom, it comes off too expensive with the sub gen 3 for me so I'm considering just getting a q990c instead and connecting a Sonos connect to it with an optical input instead , but I would never upgrade since just one sub is enough to piss my neighbours off lol so I wouldn't have any negative performance if I just keep my gen 2 sub?

So that Samsung soundbar output into the ‘Connect’ will be stereo only and it will have at least ~75ms delay due to audio buffering so I’m not quite sure what you you’re trying to achieve there?

@Barking90, 
Input from the ‘Connect’ to the q990c Soundbar will be in sync for music sources, but the Sonos Sub is then not going to be used with the TV audio output and what will you use for TV HT surrounds? 

Also note the optical connection on the old Connect is an ‘output’ port rather than input. See below:

The Samsung Q990C is a full soundbar/sub/surrounds set. Rtings rates it highly, and it should obviously work seamlessly with the TV. I can understand the quandary.

Ah thanks @ratty  I thought it was just a Samsung Soundbar and that the OP was perhaps looking to somehow use the ‘Connect’ with the Sonos Sub gen2 and Play:1’s as part of the HT setup, but makes sense now..  That will teach me to dig much deeper into these things.

Its also half the price of getting an arc and two era 300s is the reason I asked I'm either gonna get the arc and eras and go broke or keep the playbar and ones for a while, And then upgrade to whatever Sonos releases next year (like a Sonos arc pro or something) If I get the q990c  I can get a port with a coax to optical converter or a connect gen 2 and use an optical to connect it to the soundbar (for living room music etc seamless with my play 3 in the bedroom) as a workaround it won't sound as good as the arc but it'll still be an upgrade from the playbar I think

Also any hardware revisions of the arc ? I may buy it used if I can find it, also I need a good speaker stand for the era 300 s they only sell ones made for one and one so, may get a universal one

I don’t believe there have been any significant revisions to the Arc since its launch. Nothing mentioned on this forum, at least. However, perhaps check the Sonos refurbished site, as all those products come with a full manufacturers warranty (which can be extended too). See link:

https://www.sonos.com/en-us/shop/certified-refurbished

Can I use a Sonos port with a coax to toslink optical adapter and plug that into my soundbar to use it for multiroom music? It'll be regular music and shit not atmos but still it would work with q990c right? Q990c will be an upgrade over the playbar and I can use the playbar and sub in the old tv at our summer home

I haven’t (yet) had a chance to watch it but I stumbled on this comparison too…

Yes, no reason why not. If you check Amazon and other similar sites, you will find plenty of those coax to optical converters to choose from too.