The Utopia hits all the right spots for me. Sweet upper range, lots of detail. Very upfront presentation. Accurate, punchy bass which is really IMO not lacking at all.
Compared to Abyss:
Abyss has much more bass. Tonnes of bass which is also accurate and punchy. Thumping bass, to the point of chest rumbling. The bass never leaks into mid range. Mid range sounds just a bit thin/hollow. Highs are detailed. But seems like whole mid/upper range is recessed; utopia singer is in your face, whereas abyss singer is maybe several feet away. Vocals have a bit of an echoey/in the box sound. Also, very finicky with positioning on your head; find the sweet spot and it's all good, but shift a bit and u can hear change in sound, such that it almost seems like there is a subtle time delay between L and R driver. Tilt the headphones a bit forward or backwards and bass becomes boomy/loose or suddenly severely lacking . Funny headphones in that when I raise the volume, I can hear the mids and bass increase, but the highs seem to stay relatively low volume.. Whereas with utopia, increase volume and the highs goes up first.
Speaking of the Abyss... I had similar misgivings with the mids when I had the Phi CC: A little thin, almost scratchy-sounding even, and generally too unsatisfying to bother with going through the effort to make the headphone's marginal, finicky fit work out in relation to its variable bass behavior. So I let them go after not so long.
Interestingly though, with the Phi TC, that main criticism is now a non-issue, at least to my ears. The rest of my signal chain is completely different than that first time around though also. Tonality is even and not offensive to my ears in any region. I'm especially impressed at how clean and undistorted it sounds. And the bass, of course, is the Abyss's killer app.
However, the sense of realism conveyed by the Utopia driven by the right amp is still unmatched to me.