Hi @Silvajay
Welcome to the Sonos Community! And, apologies for the delay.
Wondering what the best plan of action for optimizing my set up and hardware for a home theater? Btw I recently moved into a home that came with everything in it which is why I have a kinda disjointed collection of Sonos products.
You will need more devices, so which course you take will depend upon your budget.
From the research I've done it seems I could potentially use the built ins as surround speakers for the arc if I get an amp (I currently have an origin DPS2-200 amp). Do I HAVE to get a Sonos amp to use these speakers as surround sound? and is this recommended vs say just getting some 100s or 300s for the living room (idk what type of speakers are in the ceiling)?
Yes, to use passive, third-party speakers as surrounds for a Sonos Arc, you would need a Sonos Amp.
A pair of Era 100s would be around about the same price as a new Amp, but they are likely to match the tone of the Arc more accurately than third-party speakers will.
Or, you can purchase one more Five and use two Fives as surrounds.
A pair of Era 300s, on the other hand, would result in the best surround sound that Sonos currently offers - each speaker has up-pointing and side-pointing speakers to better immerse you in Atmos audio. The cost will be higher, however - roughly twice that of the other three options (seeing as you already have one Five).
Any of these solutions would leave you open to adding one Sub or Sub Mini, or two Subs, at a later date.
My 5 is somewhat redundant now. I'm thinking of selling and getting a sub to go with the arc. Good move or am I selling it short? I can play TV sound thru the Arc, the 5, and the built ins at the same time which is cool but not really accomplishing anything (other than having tons of stereo sound throughout the house).
That’s entirely up to you and your budget considerations. Sonos systems are entirely modular, however, so you could opt for one of the setups above and try things out for a while - should you feel you want more bass, you could perhaps find a second-hand Sub for around what you might get for a second-hand Five. Or, you may have found by then that you really like having the Five in your Kitchen or Bedroom and opt to keep it after all.
Bear in mind that if you ever go for dual Subs, one of them must be a Gen 3 Sub.
The Port that you have cannot be integrated into a Home Theatre setup, but it can operate independently on the same system.
There are no right answers, basically, but if you have more questions, please feel free to ask.
We have official eBay stores where you can buy second-hand Sonos products that come with warranties:
I hope this helps.