The best thing to do is to add subs. I think you and I discussed this before, but just to be sure I'll hit the high points. The idea of adding subs isn't just to augment the low end but also to smooth room modes. Having just two subs added to the two bass bins you already have will give you four bass sound sources. This smooths room modes by averaging, filling in holes and partially cancelling peaks.The Omega 15 can be used in cabinets from 2.0ft3 to 5.0ft3 tuned to 40Hz. It works great in a four π cabinet, so you could make one of those and place it between the speakers you have now. However, I think for a dedicated subwoofer, I'd prefer it in a larger box than this. You can go as large as 8.0ft3, tuning a little lower to 30Hz, and get a nice EBS alignment. That will give deeper extension and will blend nicely with the bass bins you already have.