Ideally, all of the speakers (front or rear, except the subs) should be at ear level when seated in the chair of choice. Should you decide on an acoustically transparent screen the the centre speaker should be placed behind the acoustically transparent screen. Even if you're using an acoustically transparent you should cosider placing the left and right speakers beside the screen (obviously dependant on the size of the screen and roon dimensions) to provide good left/right separation and depth.

Other issues to consider is seating distance from the screen. You don't want to be sitting in a null point.

Cheers