I agree with Hutz, you would be much better off treating your corners with Bass Traps first, followed by a few first reflection panels. You don't have to do the superchunks like I did, you can just straddle the corners with panels (at least 4" thick). Treat the 4 corners first, then if you want, some people also treat the corners where floors and ceilings meet the walls.
Also, I assume you have carpeting on your floor? This makes a world of difference if you add padding/carpeting. If not, you need to at least have some throw rugs down at the first reflection points.
Also, the best position in the room with the least nulls is one that is 38% from the front wall of the total room length. Second best is 38% from the back wall. 50% is the worst, or if your right up against the back wall.
Anyway, it would be much cheaper to just build some panels. I don't see how making the adjustments that tech gave you will help with peaks/nulls.
Now, I did build a riser stage for my speakers to sit on and filled that with thick insulation. Many people don't realize that in some instances, the low bass from the speakers can actually travel through the floor and arrive at the listening position faster than the direct sound.
