I'd say 4 meters depth would be a minimum for the Def's to truly shine. The Druids can work with less, no doubt.
When I decided to upgrade my Def's to Pro's, I needed to EQ. The TacT played alright with the Modwright, but the combination seemed to give up some transparency so I decided to use the TacT as preamp. That caused a tonal shift toward the neutral/clinical that I'll try to cure with a good SET amp.
With all the shifting, I couldn't afford to keep the Modwright either. It's playing a happy little song in California now.
Thanks for the kind words. Seattle's a great town and I'll be here for a long time. And, we're all in this hobby together - respect and civility keep it all enjoyable.