Hi -
I have iQ5s and iQ6c. For the sake of an harmonious ralationship, not to mention harmonious living room acoustics, I went with Kef in-ceiling speakers ci160qs. As I understand it the cones are the same as those used in the iQ5s, and are Uni-Q also. They look fantastic, are virtually invisible, easy to install and sound great.
Not only that but I believe it helps create a much more expansive rear sound "picture" if the speakers are higher up.
Cheers.