After a few more days of movie watching with both tapped horns in the system, I must now conclude that adding another horn was exactly the right decision.
Watched Unstoppable the other night. 118dB sustained at listening position... not only did the two monsters have the power to move my pants legs, but my hair as well. That's a first in this room. Got up several times to monitor excursion. At no time were the SDX's moving more than an inch peak to peak. Nowhere near Xmax. Same with the Tang Band horn. All this with only 700W. I have silly headroom now - gotta love it
Some have been asking me for more detailed plans for the Tang Band horn. Since there's now been enough interest for me to spend the time to do that, I'll whip up a Sketchup model for that one as I have the time. I still don't reckon many people if any at all will try that one. I'm now confident the bracing can be omitted from it, too, but it's never going to be as wood friendly as this SDX project is.