I recently put in a pair of the Polk RTS 100 ceiling in a fourth system in my house (living room). The electronics are tubed SET, DAC, and sonos, all hidden in a cabinet. I absolutely love the sound of this system and the Polk speakers( I have not demo'ed any other in ceilings.) I think the Polks are hard to find since they are no longer made. However, a friend found a pair after her my system.
Hope this helps.
Hope this helps.