Polk Signature Series and In Wall

Hello,

I am looking to put together a 5.2.4 system for my living room. I was thinking the S35 center and a pair of S15 or possibly S20. I like the S15 for aesthetic purposes and I am sure with a couple of good subs I may not question "What if" with not going with the S20.

My main question though is what series of in wall speakers would be good for the surrounds? Also for the 4 in ceiling atmos?

Thanks