A lot of great advice and opinions to consider so far.
Pauly -- I'm using a really cool little room organizer web application that I found on a furniture site. Here is the site:
http://raymourflanigan.com/room_planner/resources/icovia.aspx
If you register with them, you can save multiple room designs which is really cool. It's great that you can use it without downloading anything (it's a Flash application), and you can specify all of the dimensions of everything you put in the room down to the inch.
Ted M Brady -- That is a fireplace behind the listening position, no doors on it.
Winstonsmith -- I have definitely noticed the bass response being variant at different spots in the room. The listening position is currently a vacuum with no bass in it, and about 3 feet outside of the listening position in any direction the bass is very strong. It is a major problem.
Chronic -- There have been maybe 30 hours of listening on the system since it was re-arranged. I'm a little worried about the "settling in" effect, because I personally believe that the settling in may actually be me forgetting the great sound I had and just getting used to the new sound.
I like Eldarado's idea of having removable acoustic treatment. I'm considering putting small patches of self-adhesive velcro on the walls in spots where I need acoustic treatment, and put the other side of the self-adhesive velcro on the treatments themselves, so I can instantly put them up or take them down.
-Dusty