@ratboysr, I may be wrong but I get the impression you think it necessary to have all subs in a multi-sub set up exactly same model. You are free to use a different type and in fact may prove beneficial. For example when helping a friend with 3 subs, 2 of them 10" and 3rd 12" my measurement showed a stubborn partial null at about 70Hz. Floor space was a bit lacking so I brought over a 6.5" little sub in a 9" sealed cube. After some experimentation found it worked wonders placed about 4ft off the floor on a large bookshelf. Measurement confirmed the the null had improved from -10dB to -4db. The small sub was about 5ft away at almost ear height so would not need much power but received enough to further smooth out the room response. In fact when turning up the volume on this sub I could fill in that 70Hz completely but raised a nearby peak a couple of dB. I erred on the side of caution to protect the 6.5' driver.
Generally it is best, for easier integration, to stay with sealed boxes. Multi - subs are transformative and I am constantly surprised by the reluctance to accept/ embrace the concept.