How do you distribute the subs? Can they all be on the same side of the room or on just two walls?
Well mine are just on two walls and work just great. I've moved them around experimenting a bit but with my system its almost impossible to have one on each wall. Well I could by putting one or two up near the ceiling! Which by the way according to DBA theory would be better. In practice however mine works so well I just can't see going to much effort trying to improve it.
Mine are on the left and right walls, each one a different distance from the corner. Plus I have one powered sub almost exactly in the front left corner. None of these is localizable, to the extent I often times have to touch the cone to be sure a sub is really working. Really low bass is amazing- it sometimes is so diffuse you feel the whole room immersed in it, yet other times its imaging the drum or bass guitar precisely on the stage right along with everything else. Seamless.
Tim aka noble_100 has a room almost identical to mine (one foot less each way) and he went through a very definite procedure to locate each one, which as I recall resulted in one very near each corner.
Remember speaker location is only half the equation. The other half is listener location. The other 50% as Yogi Berra might say is having four.