Well gents, I promised an update after hearing a local audiophile's Avantgarde Duo Mezzos a few weeks after Duo XDs.
The Mezzos were in a medium-sized living room with tube traps in the corners. This was an analog-only session with both Clearaudio/Anna and Galibier/GFS combos through a Zesto top of the line phono into a CJ GAT preamp and then ultimately through Nagra VPAs with Psvane 845s.
The Mezzos are quite a step up from the regular duo in cabinetry - its a large speaker and takes up some good real estate. The owner had them 3-4' out from the back wall, so not carved into a corner like some AG setups. The AG hallmark sound was easy to discern - big, open, dynamic with that very live soundstage feeling. In fact, most of my impressions from my XD demo were still present despite very different rooms. The Mezzos definitely propel sound in a visceral manner and don't quite image or disappear as well as other topologies as I've stated before. Its really fun, exciting sound. What I did notice different from my last demo was that the bass notes were more natural sounding on the Mezzos - i quipped with the owner that they made the regular XD sound a bit "subwooferish" in timbre. Interestingly enough, while the notes were more natural I'd still give the edge to the XD in overall integration.
The AGs displayed good tone on my Everything but the Girl cuts - in fact, that was arguably the best demo I had from the session. We also switched between analog rigs and I have to give the edge to the CC/Anna as it had better flow and was more even top to bottom. I did find the Nagra 300b amp on the XDs a bit more rounded and convincing than the 845s - not that it was a huge difference, but just that last bit of synergy.
Overall, this was a fun visit and one where I could go home later and hear the pros and cons of horns vs. DeVores. I'm still formulating my thoughts, but on first blush horns give an astonishing quickness and soundstage that brings the performers to you (borrowing a phrase that my friend who was there with me said afterward). Also however, I've noticed in both demos thus far that I haven't been able to fully relax. Whether that is the jump factor, dynamic swings, or raw energy I do not know. But I am cognizant of this feeling.