Odd-shaped control room

The control room in my studio / house is sort of L-shaped and I'd like any advice you people might have as to where I should situate my desk and any additional acoustic treatment you might recommend that would help improve the consistency and accuracy of the room. The rectangular portion of the room has an angled ceiling and was added to the house sometime in the 80's. The portion of the room with the lower, 7' ceiling is part of the original structure. The smaller area with the 7' ceiling has a hardwood floor whereas the new portion of the room with the higher, slanted ceiling is carpeted. Currently the desk is in the portion of the room with the 7' ceiling and the engineer's chair sits on the theshold between the sections of the room. This can be seen in the photograph I've attached. (Sorry about the poor quality.) My biggest complaints are 1. An uneven-ness of bass response which varies a lot from place to place within the room. 2. A small "sweet spot"... With the engineer's head being on the threshold between the part of the room with the 7' ceiling and the part of the room with the 9' ceiling, slight changes in the listening position effect what one is hearing fairly drastically. I'd like to make the "sweet spot" larger and currently it's hard to tell where that "sweet spot" even is. Current treatment... Before I moved in, the walls in the area with the 7' ceiling had been been stuffed with pink insulation and covered with approx 3/4" thick fiberglass panels. The ceiling in the 7' area had been stuffed with about 6" of pink insulation, but also covered with thin plywood with fiberglass panels over it. I left all of this as-is. About a year ago, in an effort to tighten things up and even out the bass response, I made corner traps and placed them from the floor to ceiling in two corners of the area with the 7' ceiling, from the floor to the ceiling in the corner behind the mix position, and where the back wall and ceiling meet behind the mix position. The traps were a big improvement but I'd still like things to be better. I guess what I'm wondering is... 1. Is there is a better place to put the desk than where it is now or should I leave it? If I leave it, should I try to make the 7' ceiling more acoustically invisible by removing the plywood and replacing it with fabric? 2. What else could I do to improve things? I'd like to keep the budget under $1000. Thanks!

Neil - I think the reason your sweet spot is narrow is that after the line of your desk the room changes shape. i.e. it's ok up to the line between the two room sections. Have you tried placing a false wall like this?? cheers john

Sorry I didn't respond to your reply sooner. There's been a nasty stomach flu going around here and I ended up getting it the day after I initially posted. Thanks for the false wall suggestion. I hadn't really thought of trying that. I'm going to try it out and see if it helps.