Thanks for the input so far. The window behind the speakers has vinyl vertical blinds that run top to bottom. I'm assuming those will work pretty much like the cellular shades. The speakers are sealed enclosures so there are no rear-firing tweeters, etc.
As far as additional room treatments I'd love to be able to spend $1k on them but right now that's not going to happen. We sit on a couch that is up against the wall opposite from the speakers. The good thing is the couch is slightly overstuffed and is long so it does cover alot of the wall length. Are there any wall mountable DIY treatments that others have had success with?
Also, given what you know about the room and our equipment/listening preferences are there any speakers (<$750) that might be worthwhile looking at as replacements for the Altecs. We could go with smaller tower as well as bookshelves on stands. The maximum we can really move these into the room would be about two feet off of the wall.