With a 13 foot square room, and hardwood floors, you're getting huge problems in the mid-80s Hz, a really important and heavily used bass range, probably near where your subwoofers' crossover is, as well as about 170Hz and probably other multiples of 85-ish. I doubt it's the size of the speakers that's the problem.
Get out of the middle of the room, maybe about 2/3 of the way back from the front. That will probably help, although maybe not a lot.