The Sonos Amp does have a line in, but what you really need is a line out.  The Sonos Port is the only device with a line out that can send an audio signal to your Costway speakers.  You can an amp and port grouped together to play the same audio at the same time.

If your plan was to send audio (and/or karaoke) to the Costway speakers, then line out to a Sonos amp, or any other Sonos product, that won’t work.  Sonos has a slight delayed needed for wireless multiroom audio, so you’ll hear an echo.

I’m not sure what your basement layout looks like, or what you’re intended use is, but 4 ceiling speakers + 2 different brand powered speakers doesn’t sound like an idea setup.  If you just want background music, or there is no real seating area or sound stage to the room, then the ceiling speakers should be ok by themselves.  If you do have ca sound stage, then a pair of speakers located there would be ideal.

Danny, appreciate the insight. The basement is relatively small with a couch, bar and pool table so no main stage. Plan was to have the two main Costway speakers playing and the 4 sonos speakers in the 4 corners of the room. I would like to send music to either the sonos amp or the costway, doesnt matter to which as long as all 6 (2 costway + 4 sonos) speakers play at the same time. How would my set up look to achieve that?