I look at it as two different speakers for two different uses. The BSSE is a ported sub while the Wedge is an OB sub.
The BSEE (since the open back acts like a port) could use the regular 8 Ohm non-OB version of the drivers and the HX300 amp without the open baffle shelving circuit. And because it is not OB can be placed closer to the front wall. Also, the sound is that of a ported sub rather than an OB sub.
The Wedge is OB so it needs the OB version of the drivers, the OB shelving circuit in the amp and needs to be at least 3ft from the wall. For this it rewards you with the OB bass sound.
The questions are can you mix and match? and if so, what are the results?
I have have/had all four variations here 1) non-OB top with non-OB bass; 2) OB top with non-OB bass; 3) non-OB top with OB bass and 4) OB top with OB bass. I currently have situations 1, 3 and 4 set up in different rooms.
The living room has N3TL's matched with a 12" sealed servo sub (1); my room has the Wedgies with the 12" Wedge basses (4) and my grandson's room has a pair of ported PSB Image B6's with the OB 3x8 H-Frames (3). I had situation 2 for six months after building the Wedgies before building the 3x8 H-Frames.
Personally, I prefer the sound of like with like best. If the room and usage support OB that would be my choice. If circumstances were such that OB could not be used then you wouldn't be able to mix and match anyway. Situations 2) and 3) make sense if the room will support OB, you already have a non-OB half and your budget won't allow a full jump to OB all at once.
To my ears, when there is a mismatch part of the sound is huge and expansive while the other part is diminished. When the midrange and treble is ported (I don't have any sealed monitors right now to try it with) the bass tends to envelop the midrange and treble. Not overpower it exactly, you can dial down the subs (which I really had to do since their sensitivity is higher than the monitors) but the midrange and treble sound more like it is in a bubble with the bass surrounding it.
A similar situation exists when the midrange and treble are OB and the bass is not however the perception of the sound is different. The bass is not as expansive as the midrange/treble. Not surrounded by it like the previous situation, but more like the bass is the floor with the midrange/treble stacked on top and around the sides rather than blending as a whole.
When comparing the two mix and match scenarios, I think a non-OB servo controlled sub mated to an OB top is going to blend and sound better than a non-OB top mated to an OB sub.
I hope I am making sense here. It's hard to describe in words. When listening to the different set-ups it makes perfect sense but when I try to describe it, not so much.
Mike