I think the BA, in PX4 (or even in 300B), was too "true" to be a good match for an un-modded HD800. I also felt the HD800 still needed some massaging with the BA.

The ZD has the euphonic luxury ride thing and the older non-SE ones with the soybean caps were even a better match with the HD800. The EC 2A3 was, well a 2A3. The S7 was also a better HD800 match because of the infinite tube rolling options.

Even the latest EC amps 4-45 (and 2A3mk4) actually have a slightly more relaxed sound compared to the BA.

Hmm, now I do wonder if it was the silver in the BAs with the EP transformers.

"Do I have the right setup in terms of amp/headphone period?" This can only be answered if you've had opportunity to switch in a whole boatload of different sources into your system to know what is the right setup. Until you do that, you're in a merry go round situation on both amps and headphones potentially. Now, marvey, you've had ample opportunities to listen to a LOT of gear, so you're actually in the best spot to answer your own question. (I know, I know, it was a topic of discussion for the REST OF US to contribute to. I'm sure you probably know the answer to your own question.)

I think our environments are also a factor to consider. ie. the quality of power, isolation of external noise, our own physical well-being at the time of listening, etc. I've been sick for the last month now and I find I can't enjoy anything due to stressing over about health, in addition to working and trying to take care of my family and young one at home. This is definitely going to impact perception of whether my system is operating appropriately together or not.

We all try to look at this from an objective standpoint, there's a lot of other intangible things going around us that we overlook. Now, I'm satisfied with my own setup at the moment because I've had my nirvana moment when a track was playing at a time of inner peace and solitude one evening. So I know the inherent potential. It's sounding crappy at the moment but that's just me not being able to get into it, mental state overloaded with worrying about things personally/professionally, etc. And the environment is a hi-rise condo in a downtown area where it's quite noisy sometimes. I can't wait to move at the end of this year to settle down in a quiet suburb of Denver, where my house already has a designated office room where I can set up my headphone system, tune out and zone out everything, and listen in solitude.

A bit of a tangent on the question overall but I do think about the environmental issue vs. just looking at the physical gear/equipment.

I presume you are just talking about dynamics here and not E-Stats

What made me happy about listening to the Levi/445 was knowing how far the 800 still could scale and how the 800 and those amps were end game for me, period.  There is simply no combo out there that can compete for resolution and transparency so I can just focus on the DAC once that's settled until a better transducer comes out.