Well, I got the woofer polarity incorrect, and I was excited that it would be an easy fix, but I read the schematic notes again, and the DE250 tweeter is also Black to +. So they're both wrong, which makes them right...
1. I purchased the JBL's new from Parts Express.
2. Not sure yet about this one, will need to connect the scope to check power output. The amp was working great with my much less efficient Zaph 5.2's
3. See above...
4. Insulation is on the brace between woofer and tweeter. Plus more lining the interior. Maybe it's insufficient? I have always added extra insulation to every speaker I've ever built during the tuning phase.
5. The port needs to be addressed. It was a fun idea but it's probably ringing a bit.
6. The room is pretty well treated. It was sounding great with my old speakers.
I do have a 12" sub which does enhance the sound significantly.
I have no doubt these speakers are capable of exceeding my expectations, just need a bit of tweaking to get there.