In wall speakers recommendations.

W(all) speakers are effected by the volume of air in the chamber, and whether it is sealed or ported. Typically larger volume = more bass.

For best results, while selecting speakers, you need to consider/locate the framing, materials, construction methods to control the vibration of all sides of the chamber the speakers will be mounted in.

I had excellent results from these Phase Tech offerings in my own home as well as a few friends:https://phasetech.mseaudio.com/ci110-siii.html
The offer larger models as well and they all sound fantastic:https://phasetech.mseaudio.com/ci110-siii.html
Plus, they're all made here in the USA!
If you have a price-is-no-object budget, check out the offerings from James, as well:https://www.jamesloudspeaker.com/categories/29

Legay Audio makes in wall (can also be mounted on wall) speakers that will sound far better than your Polks.

On wall:
https://legacyaudio.com/products/view/silhouette

In wall:
https://legacyaudio.com/products/view/silhouette-pro

Thiel Power Planes:
THIEL Audio | PowerPlane 1.2