I gave my impressions of the Immanis vs Susvara on the Feliks Envy on this other thread:
https://www.head-fi.org/threads/feliks-audio-envy.960600/post-18120782
In shorter worlds, The Immanis are a different beast (or complementary) compared the Susvaras, they are more vivid/exciting with great dynamics and slam (I believe more than Utopias) and they have some impactful, deep and unbounded bass that never experienced on any other headphone (Susvaras and Utopias lack quite bit on that department without EQ). Resolution-wise is as or more resolving than Susvaras (hard to tell exactly because the treble has a different presentation on the Immanis, a bit more pronounced which I also believe make them feel more aired). Soundtage-wise it felt bigger and more 3D compared susvaras with a superb separation of instruments and insane clarity (susvaras also but presented differently, less vivid).
I tried the Immanis on both, Envy PE and AE and is a killer combo with both, but don't ask me about differences between these two amps, they were using different tubes (stock tubes for each version).