A:AnswerNo you can literally place these anywhere. They come with mounting brackets they lock in and kind of float and can be mounted upside down or even sideways depending on the room and angles.
I have 4 sets (8 total)of these for my atmos/aura 3d and I love them.
A:AnswerWell if you have both sets you can easily try both see what you like better. Having had both the sets the svs for atmos or rear surround is a overall better speaker then the Polk in every way.
Personally I would use them as a rear surround as they sou d cleaner and atmos is not really in every format. Also depending on the receiver you have look in to aura 3d.
A:AnswerThese sound great in any configuration I have 4 sets of these for my height speakers 5.2.8 and they are beautiful for atmos also look into aura 3d similar to atmos but works with every movie I have played so far.