Matt,
Spent an interesting afternoon with Richard Vandersteen and the topic of room treatments came up. His advise is to go slow and don't go overboard with absorption. Treating the first reflection points with diffusion is a good strategy. One of his points is the room treatment guys are in the business of selling room treatments so you need to be prudent about their advise. On another note, I have never been a big fan of the foam type of diffusers and prefer wood. Our audio club just moved to a new location and the new room is a challenge with the acoustics. After bringing in all kinds of tube traps, acoustic panels, diffusers etc. the biggest effect on getting decent sound was the actual placement of the speakers in the room. We tried multiple set-ups with and without treatments. Go figure.