Hello ronboco,
I just want to clarify a few things that will hopefully help your understanding. The distributed bass array (DBA) is a concept discovered virtually simultaneously through empirical scientific experiments performed by Dr. Earl Geddes and Dr. Floyd Toole. Their basic results can be summarized as: the more subs utilized in a given room, the better the bass response performance becomes. They found there were significant performance gains up to 4 subs and only marginal performance gains beyond 4 subs.
The empirical scientific methodology utilized is important because it means their experiments can be independently and reliably duplicated by others, while obtaining highly similar results, following the exact same methodology. This is the process that establishes scientific truths or facts.
Geddes told his protege, Duke LeJeune, about his discovery and generously gave Duke his permission to use the concept if he wanted to. Duke said "thank you very much E.G.", proceeded to create a complete kit product based (bassed?) on this concept and named it The Audio Kinesis Swarm.
In turn, Duke has also been generous with this DBA concept. He readily admits that it performs equally well, along with it being scalable and likely performing even better, if a custom 4-sub DBA is created by using larger and/or higher quality passive or self-amplified subs. However, a custom 4-sub DBA will not only be more expensive, it will be more difficult to set up since the volume, crossover frequency and phase controls need to be optimally adjusted on each sub rather than just once for all 4 subs on the Swarm's amp/control unit.
I have a lot of experience and knowledge with using 1-4 subs but mainly in my 23'x16' room with an 8' ceiling. It may be best for you to first experiment with optimally positioning your 2 existing subs in your room, using either the REW or the sub crawl method, and evaluating the results. If reasonably satisfied, you always have the option to add a 3rd and/or fourth sub. You also have the option of buying a $200 Mini DSP unit which makes connecting and adjusting up to 4 subs easier.
Your choice should also be guided by whether you want very good bass performance throughout your entire room or just at a single designated listening seat. At least 3 subs are required for good bass throughout the entire room.
To answer some of your other questions, I wouldn't concern yourself with bass traps and other room treatments until you get the bass sounding right in your room. I'm also confident that 2-4 subs, properly positioned and configured, will integrate well with any pair of main speakers.
Hang tough,
Tim