Im trying to integrate my ZAPH AUDIO SR71's that are sealed, with two Dayton Audio RSS265HF subwoofers that with be sealed and be directly underneath the SR71's, I want to use some sort of active crossover filter, what would be the very best option to get the best out of these speakers? I was thinking of using a 24db/octave Linkwitz-Riley filter at 100Hz one for high pass and one for low pass, can someone please let me know the best way to crossover these speakers? idk if i need to add a all-pass "delay" filter to the SR71's or the Linkwitz transform circuit to the sub, there are so many decisions that I can't figure out what the best thing would be, your help would be greatly appreciated. 
"also what size boxes would be idea for that type of subwoofer I'm trying to get good response down to 25-30Hz.
"also what size boxes would be idea for that type of subwoofer I'm trying to get good response down to 25-30Hz.