Thanks for the replies.
The general concensus seems to be "above ear level", but how much above ear level? The ecoustics link above says "about 2 feet above ear level", but I would think it depends on how far you are from the speaker, right?
The speakers are being wall-mounted so they really can't be moved (without patching up the holes, repainting, etc) after they are installed.
Anybody have any other suggestions for me?