That is a nice setup. I agree with Dave, the towers are running full range so there is going to be some overlap in the mid bass. It is most likely integration/tuning/placement. The towers have great mid bass. If the sub is not on the same plane as the towers and if they are not level matched good you can get an out of phase or may have a room null. You should try it without the sub and you can also try to flipping the phase switch. I would personally drop the crossover down lower to 60hz range and you would proably get the tightest bass(least boomy) from the lower q setting on the amp in the .3-.5 range. Other than that you would need an spl meter and some test tones at a miminum to get the best integration or use room eq wizard and a umik mic with a laptop to see what is going on.