I have just added a Force sub to a system that already included two Titans, and thought I'd share my first impressions ...
First, the Force itself - not only is this thing cute, it is amazing in performance, especially for its size and price! Easily capable of rattling windows all by itself, and goes very deep and clean in my room.
Second, why more subs? I have achieved very good bass with a stereo Titan setup, with a Titan approximately behind each main speaker and against the wall behind. But I'd wondered for a long time about using more bass sources in my fairly large, open, irregularly shaped space (roughly L-shaped, 25' long, part 10' deep, part 18' deep, and open to a hallway, an adjoining space, and a stairwell. And, I figured, if the Force didn't improve bass in the main audio system, I'd move it downstairs to the home theater ... So I set up the Force at one end of the listening sofa.
Third, the effect of adding the Force to the existing system - with about an hour of setup and adjustment (and 3 subs allows for a lot of adjustment), I am getting bass quality that is less "thick" and has more impact. In terms of quantity, there is actually a little less overall, except at the very low end (20-30 Hz). With the 3 subs and my Behringer EQ, I've now got measured bass that is +2/-1 from 20 Hz on up. There is also a hard-to-describe improvement in spatiality of the sound.
It is obviously early in the tweaking and listening process, but it is clear that the home theater is going to have to wait for a new sub. Thought I'd post these first impressions now, partly to see if anybody else has experience with using more than 2 subwoofers in a stereo setup. Thoughts or suggestions?