I have two recommendations to make. The first is to go for at least two smaller subwoofers instead of one big sub. In most situations that produces a far more even response. See here for some reading: http://www.acousticfrontiers.com/20101029using-multiple-subwoofers-to-improve-bass-the-welti-devanti...
The second suggestion is to invest in a DSpeaker Antimode 8033 room equalization unit as well. This tightens the response significantly in both the frequency and time domain. With two subs this is even more effective because the equalization will be effective over a larger listening area. Subs have a bad reputation in audiophile circles, but this is largely due to the problem of the room modes that they excite. These not only produce peaks and dips, but they also linger on. People speak of slow subs, but it is not the subs that are slow, but the lingering room modes.
The second suggestion is to invest in a DSpeaker Antimode 8033 room equalization unit as well. This tightens the response significantly in both the frequency and time domain. With two subs this is even more effective because the equalization will be effective over a larger listening area. Subs have a bad reputation in audiophile circles, but this is largely due to the problem of the room modes that they excite. These not only produce peaks and dips, but they also linger on. People speak of slow subs, but it is not the subs that are slow, but the lingering room modes.