Are you saying you have 5 speakers in ceiling.   Is that for front R, Front L, Center and 2 surrounds or just for surrounds only.

Unfortunately, 5 speakers in the ceiling does not mean you are ready for surround sound.  Generallly speaking, you typically have 3 speakers in the front, left right and center, at sitting height level...not the ceiling.  You have 2 rear speakers also at height level.  You can add speakers in the ceiling for atmos audio, but Sonos doesn’t allow for this, using upfiring speakers in the Arc instead.  Really, you can’t make a good surround setup with your celing speakers, and maybe only a really bad one depending on where exactly these speakers are located.

You could get an amp to connect to your TV, and power the front left and right speakers with a ‘phantom’ center channel.  You can buy a second amp to power  rear speakers. ($1400 altogether) You will have TV audio and streaming music capabilities.  However, you won’t use one of your speakers and it won’t be a good setup.  You could get a normal receiver to power your speakers connect to TV, and just use a Port ($450 + whatever reciever costs) for Sonos streaming audio...but still not a good system.  If it were me, I would probably just get the “Premium Immersive Set” (Arc+Sub+2 Ones = $2000) and forget the ceiling speakers existed.  Maybe remove and sell them if you can.

Sorry, I know that’s probably not what you want to hear.