Bryan, Dean(grunt)is our member who's experimented the most with height and width speakers, so hopefully he'll see this and comment.
As to the most appropriate speakers, the height sounds are quite diffuse in nature and therefore an ideal speaker for this function would be the QS4s. You don't want the speakers beaming directly at you.
The height should be close to the ceiling and they should be directly above the mains, so the "entertainment piers" location you describe should be close enough. Some type of base to give the bottom driver a couple inches of free space should be used.
