Okay, I've signed up for a pair of JBL 2123's as well. No sense in ending up with a 2-way with all kinds of strain through the midrange as the drivers try to be things they are not at their frequency extremes.
This is no longer speculation; the drivers are ordered. I'm convinced it will turn out well, but I'm curious as to whether anyone out there has done this combo before:
TAD 1602
JBL 2123
Eminence PSD 2002 in Marintelli horn (either/or with the other 2, actually.)
I'll post further details, pics and impressions as this takes physical shape.
Keep your ears and your mind open.