I'm on a DAVE as well. Regarding the amps I cited earlier (AHB2/HPA4, AMP-13R, and Pass Labs X150.8)...
For treble I'd give the HPA4 top ratings. That was my favorite aspect of the HPA4 with the Susvara. The 13R and the Pass Labs are both a shade more modulated in that area, equally so, I'd say.
For decay, I like the Pass Labs the best. Especially late at night when the power quality is at its best for me, the sense of decay and the ability to render low-level details generally can be almost magical. The other two would be tied for second. Relatedly (at least in my mind), the differences of PGGB upscaled tracks compared to their originals are markedly more apparent on the Pass Labs than the 13R, which is something I value a lot.
For soundstage, width as well as separation is best on the HPA4. For depth, the Pass Labs amp without question. The 13R is good and well-balanced in both dimensions.
For transparency? I have lots of trouble with that word along with words like "resolution" and "realism". Each of the 3 amps presents a slightly different interpretation of the reality of a recording, which admittedly isn't too helpful.
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Of the headphones I use, I think the AMP-13R synergizes best with the Phi TC. Its smoothness and relatively laid-back character does the TC well. It's my favorite of my amps for the TC (over the Pass Labs and probably also the Cayin HA-300), and this is the pairing I've done the majority of my listening with since after my first couple weeks with the amp.
I also really like it with the Auteur, which was really a nice surprise.
The Susvara comes in third, which I both hate having to admit and took me a long time to admit, in large part due to my own preconceptions. I now kind of regret having written some slightly overly-gushing first impressions of the amp a couple months back, actually. I also had to make like four different specific tweaks to my system setup to make the Susvara sound less bright and more dynamic, which is not an issue I've ever had with any amp with the Susvara (regarding brightness, I mean). I think the 13R sounds pretty good with the Susvara generally, but is lacking oomph in the bass compared to amps with better Susvara synergy, and lacking a little bit in bass quantity generally. It's partly for those reasons that it does better with the TC for me -- though based on the criteria you specified, I could see this not being a sticking point, potentially.
Lastly, I like the Utopia least among my headphones with the 13R, though I've done very little listening to the Utopia for several months now.
