Single vs. Dual Subs

Okay, so if going with dual subs, can you mix and match sub brands? Seems like sticking with the same driver size may make a difference. I have a Paradigm x10 but was thinking of pairing that with Sonus Faber sub to pair with my SF speakers, but I might be better to go with a second x10. Integration with the same brand seems obviously a lot easier.

"Seems" and "is" are two very different things, for sure when it comes to subs. Duke makes his Swarm with plugs enabling you to convert one or more ported subs to sealed. After studying the matter and talking with Duke mine were made with two ported, two sealed. I also have a 5th sub that is ported iso-baric.  

The truth of the matter is there is no "integration" process with a DBA. You plop them down, you set the levels, they are "integrated" whatever that even means. To me it means the bass is seamless with the rest of the sound stage. This happens automatically. You could use five completely different subs or five all the same, no difference. So save your money. 

divertiti, It is impossible to perfectly tune a single sub so that it's frequency response is flat at any listening position in an enclosed room.
So, you can live with a single defective subwoofer or minimize the damage by getting two. Depending on your main speakers two may be enough.

Perfectly flat, no. With a bit of room correction on the mains, the REL B1 ran 100Hz down to 31Hz, +/-2dB in the listening seat, and the sub's location was invisible (low pass 23 and low vol).
Still, the B1 went into the home theater and now have three sealed SVS subs (3000 and 2000s) in a DBA type array, which is better than the single sub.