Get 2 subs. If your speakers could go as low as you wanted, there would be a driver in each speaker to accomplish that. For a few years I tried to integrate a single sub in my system, different ways of connecting it, even different subs, always fiddling with settings, taking it in and out of the equation. Then I got 2 down-firing subs, placed them on the outside edge (not touching) close to each speaker, on tile squares (as speakers). Tried to place them as close as I could if they were actually part of the speakers. Problem solved. They sound great and very well integrated. I am not a big bass fan at all. My speakers are rated down to 38hz. Just needed that little extra low if it is part of the recording. I am sure all the other suggestions are great, this was just my experience with 2 vs. 1. Have fun!
