And, there are a lot of very good high-performance inexpensive subwoofers out in the market today like Rhythmik, HSU, SVS, plus the higher priced RELs J&Ls, etc. I’d consider 2-4 of good $600-?00 subs, seriously.
Unless you have amplifier concerns I’d not worry about high-passing unless your mains need that high pass. For higher volume playback it might be beneficial to keep energy away from main woofers possibly. My mains run unimpeded and all subs are low passed at 50Hz (with low volume). The increased ‘air’ is wonderful.
Sorry if that wasn’t what you wanted. After fiddling for 40 years with sub ‘specs’ and technical BS I now realize the DBA concept totally runs that old thinking out of town (at least in my own practical experience, and like that of many others).