One thing I forgot to mention, specs and measurements like the one's shown above don't mean crap when you get a speaker in a room. This speaker seems to have plenty of output to 40 Hz, which is great for the size, but in the room this could go either direction.
I would proceed in this order:
- Place your main speakers
- Treat the walls and ceiling
- Evaluate
Treating the walls and ceiling will often bring out the bass to the point you don't want more. THEN if you still want more, the dual subs, placed in ideal situations with EQ and bass traps may be your next steps.