Even though I have had the Helene in my system for a couple of months now, life stuff has gotten in the way of a deeper dive of what I am hearing compared to other DACs I have owned. Unfortunately, I have never heard one of the Audio Mirror DACs so I cannot respond directly to your question.
Compared to the Mojo Audio’s Mystique X SE NCZ, which I still own and still have in my system, the Helene (at almost twice the price) moves the needle closer to neutral while still displaying the natural (non-digital) sound that I enjoy from the Mystique X SE. I perceive a bit more clarity in the upper frequencies while still providing well-saturated tonal qualities and prodigious deep bass, but without an overly apparent mid-bass boost. It is a very enjoyable DAC to listen to on all types of music, and certainly one of the two best sounding DACs I have owned, if not the best.