plavosn,
I have IB1s and the dedicated IB1 center in my 13.5 x 18.5' room and they sound fantastic. They are setup along the long wall so the left, right, and listener form an 8' equilateral triangle. I haven't heard the OB1, nor the IB2 so I can't comment on those models. I have tried an 8B-ST, 3B-ST, and 4B-ST with the IB1's and have found I prefer the 4B-ST which seems to provide more authoritative bass. I haven't heard the SST line so I can't comment.