Room Treatments to Minimize Interactions

Could use some recommendations on where to start with room treatments to optimize my new speakers, they are the VA Mahler. My room is 33’ wide by 21’ deep. The speakers are currently on the long wall about due to room usage issues. The speakers are setup about 18’ apart and 19’ from the listening position. With this layout I am getting very good sound-staging width and depth. The speakers are 3’ out from the back wall, which is sheet rock (I can’t move them farther out due to traffic flow through the room). My listening position is a large couch, with overstuffed pillows, up against the wall opposite the speakers, so my head is about three feet out from that wall, which is a series of glass windows that open partially into another room. The ceiling is 10’ and flat. To be precise, due to the number and size of openings in this room on most of the walls, the 33’ by 21’ size is rather understated. There is a wall to wall built in bookcase to the right side of the speakers, about 6’ away and a free standing masonry fire place that opens into another room on the left, about 5’ away. The only furniture is a couch, loveseat and coffee table opposite the speakers on the listening position side of the room. Both the wall behind the speakers and the wall behind the listening position are fairly reflective. This is likely way more information than most of you want to hear, but I thought it might help someone give me a starting point.
Get ahold of the Chris at ASC (acoustic sciences corp) at I use their products and think they are well worth their cost. Chris can help you with your specific room and set up.
I agree very much with ASC, though unless I'm mistaken, Chris has left and you may deal with someone else. I also have a room with openings into other rooms, and I find I have to treat selected surfaces in adjoining rooms too. ASC is not cheap but its highly effective.
I also use ASC tube traps and panel diffusors with good results in my 14 X 22 ft. room. 33 X 21 Ft. is an impressive room size. You should have lots of options in that size room. Good Luck. Craig
I'd start by reading F. Alton Everest's "Sound Studio Construction on a Budget" (which covers listening rooms too) or his "Master Handbook of Acoustics" 4th edition, to learn about room acoustics. If DIY treatment devices interest you and you have workshop capability, email me for instructions for DIY RPG-style diffusors and Argent Room Lens clones. A Jon Risch web site has instructions for ASC-type bass traps.
If you want to save money goto the acoustic treatments section.
I agree with Tom, I use the Jon Risch DIY bass traps work very well to curb the bass in my room. Jon is very knowledgeable about room and recording studio acoustic problems.

At least read it for yourself

More info in Audio Asylum.
Thanks to all for the assist