....now that you've sold your subM's....did you end up getting dual OS's?
Man, it was close! I had emailed and called Jeff and he completely lived up to his excellent reputation. I had a list of questions and concerns and he addressed them very patiently. It ultimately came down to aesthetics and also the worry and conquest of missing out on <20HZ material.
I ended up going with three custom dual opposed 18" sealed subs (6 total 18" drivers) that are being made by Jeremy with Reaction Audio. I am hoping they give me the output above 20HZ (the nice tactile chest thump) along with the ULF that I just didn't want to give up on. I realize that Cap S2's were also an option and they too were on my short list of: 1. Orbit shifter lfu's 2. Custom Reaction Audio dual opposed sealed 3. Cap S2 4. DIY. 5. Waiting for the Submersive XL's to become a reality. Being very familiar with the sound of the sealed, dual opposed design of the SubM's that I sold, I felt it was a logical evolution to go with a similar design with larger drivers, more drivers, and more output.
Thanks to all of the advice of the JTR experts on this thread!