Hopefully your ceilings are tall and flat. Mine are cathedrals and I'm convinced this is one of the worst configurations possible to manage for great audio. The RMAF website has videos of an interesting dialog on the subject with Jim Smith (Get Better Sound) and Charles Hanson (Ayre Acoustics).
http://audiofest.info/2011/video_player.php?video_id=21&Sid=fec2d4851b7bef5ad0631ad20a7e25bd
Best,
http://audiofest.info/2011/video_player.php?video_id=21&Sid=fec2d4851b7bef5ad0631ad20a7e25bd
Best,