I put QS8's on adjustable stands from GoodGuys. They go up to 48" inches - about 5" above my head seated. They sound awsome as far as I can tell - they are back mounted so the bottom firing woofer is not obstructed.
Since I haven't experimented with wall or ceiling placement (wife won't allow it) I don't know how much of an improvement it would be. From what I was told, these surrounds are very flexible. I am sure some residents here will give you the technical aspects of your placement and why they should be mounted.
