Sorry I didn't see this earlier, somehow missed it.
Here's a great article on room modes, but unfortunately they never finished it with a part 2, but it is a great primer on the subject:
http://www.audioholics.com/room-acou...om-acoustics-1
If you enter your room dimensions into the calculator, you will see that there are a lot of zeros on the adjacent mode spacing column, and that you have modes at 31.4, 62.8, 94.2, and 125.6 Hz that are all evenly spaced. You don't want this as it creates cancellations at those frequencies, and that is really what a room mode boils down to. Dave or someone else please chime in if I'm wrong, but this is how I understand it.
If you compare that output to a room that is, say, 19 x 14 x 9, you'll see that there are no modes which are adjacent, IE, the adjacent mode spacing is never 0, which means that those frequencies will not tend to be cancelled nearly as much, and you'll have a more consistent frequency response as a result.
The only way to effectively combat difficult room modes is through multiple subwoofers, room correction, and bass trapping.