On the other hand buying new speakers is easier, it feels really good hitting "submit" on that order, and it's great fun unpacking them and trying them out
. Seriously, you have real nice speakers already. Going to bigger mains would make a slight difference but I don't think anything you have is the weak link today.
Have we asked about the wall / floor finishes and how much soft furniture & drapes you have in the room ? First thing is to sit in the "sweet spot" (you DO have a nice chair in the sweet spot, right ?). Get a mirror and an assistant if necessary, but figure out where the first reflection point is between your ears and the speakers, ie where on the wall and floor does the sound bounce off when going from the speakers to your ears.
Make sure that (a) the reflection spots aren't all shiny and reflective, and that (b) the two sides are similar, ie not real shiny on one side and soft & fluffy on the other side. Think about rugs and wall hangings. Drapes. Icky stuff. Carpet or rug on the floor is good but lose points for a big glass-topped coffee table between you and the speakers.
If the family permits, you can get cool foam panels for the wall which look real sharp if you are an audio nut, and look like overpriced packing material to everyone else.
Your room shape is pretty good but the room modes are right where you called them -- 44 Hz is the peak from the 13 foot dimension. I *think* you are making that peak worse by having the speakers at the 1/4 and 3/4 mark due to the doors -- can you try pulling them further apart and see if that helps ? I know you can't leave them that way but it would be good to know.
The modes would also indicate a dip at 120. I can't think of any easy placement tricks to counter the dip at 120 or the peak at 130 but a bass trap or two would probably help the whole range.
Look at
http://www.realtraps.com.
Edit -- I fixed up the picture on the previous page to match your room and took the liberty of hanging a couple of HF MiniTraps on the wall. The HF traps are normal bass traps which also provide absorbtion at higher frequencies to help with reflections and improve your soundstage. Two traps aren't enough to make a huge difference in the room acoustics but they will definitely help, and you would be pretty much killing two birds with one stone.
Note that the traps are located so the HF absorbing surface is at the spot where sound from the speakers would bounce off the wall and arrive at your ears a bit delayed, mucking up the imaging.
