This’ll be a bit random/jump around some, but here we go …
If it was me, I’d wait on any prospective Abyss purchase at this point. It is a model that has been periodically updated, with the most recent trio of updates coming about 18 months apart. And that’s almost where the latest TC version is in its lifecycle.
Ergonomic/comfort and power-hunger issues aside, they’re great headphones. But I sold my Phi CC set, am passing on the TC, and will wait to jump back in until its eventual successor arrives, regardless of whether that’s three months from now or three years for now.
And it is, of course, possible that no successor to the TC happens (JPS-Labs could go in a different direction, introduce a higher-tier model, or just stand pat for an extended period - as with the original AB-1266). But since I like what I have better than the Phi CC or TC, that works for me.
The Meze Empyrean are a gorgeous, beautifully made, easy to drive and incredibly comfortable headphone. They’re popular for a reason.
I personally find them lacking coherence, with a disjointed low-end and beam-like treble with a just-too-recessed-for-me mid-range, and much prefer the sound of the RAD-0.
While I could certainly have purchased both, and have had both on hand to compare together, it was pretty apparent to me that having the RAD-0 would mean I wouldn’t use the Empyreans, so I passed on buying a set. I would still rank the RAD-0 ahead of the Empyrean sonically, with the Empyrean being better in every other regard (except perhaps aesthetic preference depending on the RAD-0 in question).
If we’re just talking sound, I’d generally put the AB-1266 Phi TC above the RAD-0, and the RAD-0 above the Meze Empyrean. The RAD-0 has the most natural tonality of all of them. The Abyss is the fastest, most resolving and has the best bass performance.