@WaveTheory
You're running what we would consider obsolete gear.
The Berkley S2 DAC is an old design, DAC's have come a long way since circa 2012. This is most likely the largest flaw in your system, the source, no getting around it.
The V281 amp was not exactly designed with low efficiency planars in mind. It's a current limited high voltage amp by design, that was their schtick back in 2014. The power supply is all voltage, not current, when it runs out of current, it runs out hard. It's why when you go down in impedance, the amp outputs less power. It's a wimpy power supply as current goes. It's definitely not an amp you see ABYSS AB1266 Phi TC or Diana TC owners using.
Here in lies the issue. If you're trying to review headphones at this level, experience aside, you must have proper ancillary gear for the job. Otherwise, all that video bandwidth is nothing but useless blabber describing the sound of an incompetent system being called out by the headphone. This, and you've never really explored the headphone's capabilities beyond another. There's no learning curve here.
On another note, had you done some homework and spoken to anyone in the community prior to publishing your
dilemma with negative reviews, someone if not I would have steered you straight. There are
plenty of ABYSS owners here, threads devoted to each model to easily see what gear people are currently using. These are targets you should aim for, and if that fails you, companies such as ours have email, social media, and a telephone number where you can communicate with extremely knowledgeable and passionate people.
Try it sometime.