Hi Scott,
I saw your post about this in the other topic I started, but didn't get a chance yet to throw in my 2-1/2 cents worth. My thinking (and maybe I'm wrong here) would be to have a sub that develops the lows a bit slower than faster as I'd maybe assume a sub that belts them out quickly may be a bit too boomy or inaccurate to what actually happens? Just a guess though. I do know or have at least heard that for the very lowest notes of a given organ the notes generally take some time to fully develop as they interact with the surroundings.
I was at an organ demo up in the loft a number of years back at the local very large Cathedral here in St. Paul, MN and when he hit the very lowest 32' on the pedal you really didn't hear anything at first, then just a rather faint, slow fluttering almost like a slow pulsing wind going past you.
Marc