Hey!
Yup, Oldie but Goodie. Don't underestimate older stuffs. Some can still compete well or even better than some new stuffs today.
I think I know how you feel coming from low efficiency Maggie to much higher efficiency JBL. Everything just sound faster, lively and more dynamic impact? Make the Maggie sound slow and a bit muted right? That how I felt when I finished my Single Driver speaker based on 94dB 6" Fostex driver. Although, I have to say that I'll always have a spot for Maggie in my heart though.
Well, enjoy. And perhaps a little experiment with upgrade like xover caps and dampening the horn might improved them. Just make sure you can reverse the process if you don't like after.
Buddy