Griffith:

Here are a couple of articles with good advice on speaker placement. The first is by Axiom's Alan Lofft : http://forum.ecoustics.com/bbs/messages/34579/129023.html

Here is another article that I have bookmarked as having more good advice for speaker placement : http://www.gcaudio.com/resources/howtos/speakerplacement.html

These probably give better advice than I could give you. I've used the information in both to help set up my M80's and QS8's. I'm sure others will chime in with other suggestions.