well the first question is do your actually NEED room treatment? if not i wouldn't waste money on it. as far as lower frequencies go room treatment can only do so much and personally i would not recommend it unless it is an unusable room because it is only going to help so much. secondly, what do you actually want for your system? there is a multitude of things you could get to improve it. if i understand your system right it is a pair of active monitors and a sub with a busted crossover correct? if i were you the first thing i would do is either repair your sub or get a new one.