The beginning of another maddness!
What can I say? They sound AWESOME! I find myself in a position that someone else (sorry, I can't remember who) on the BASS list remarked on. I'm going to have to relisten to my ENTIRE music collection again to hear what I've been missing!
I am not able to do any scientific testing or measuring for now, but that doesn't bother me much. It's QUITE clear that these subwoofers are doing the job WAY better than anything I've had before!
The first listening tests I put through them included sine and warble sweeps starting at 10Hz. There's usable output beginning at 20Hz, and coming on real strong between 25 and 30Hz, but it's the visceral impact that I wasn't prepared for. Watching those drivers move so far in and out of the box was quite a show! A friend coming home while I was feeding these tones, felt the concrete walkway at the end of the house vibrating! He didn't know what it was until the next day when I talked to him.
Many thanks to all who helped me out with recommendations and tips. I'm sorry I couldn't implement all of them, I'll just live with this effort until next time.