IER-Z1R

In a nutshell, Tia Trio's wow factor lies in its bass response while U12t's wow factor lies in its imaging. I found the upper treble peak on the U12t its biggest weakness and likely its most controversial aspect, but it's no worse than the IE600's upper treble exaggeration. Truth is, the 'reference-adjacent flagship' sound the U12t targeted has mostly been done better by newer IEMs such as Symphonium Helios or Subtonic Storm. Meanwhile, the Tia Trio's bass is only rivalled by (IMO) the IER-Z1R and the astronomically-priced Brise Audio Fugaku, but both have an even more coloured overall tuning. The common reviewer consensus is that 64audio's A line tends to have excessive bass that makes it sound unbalanced compared to the U line; this makes sense in a loud live session, less so in casual listening. Not exactly an issue if you plan to EQ though. If you've been EQing anyway, may I recommend the dark horse (and my own daily) that is the 7th Acoustics Supernova. Bang-on neutral bass and treble with a relaxed (some would say honky) midrange that could easily be EQed to whatever you want thanks to its smooth frequency response. Resin shell is on the medium-large side but it sits in my ear comfortably, good isolation because of the fit, but even aside from the midrange, its other weaknesses are possible 8k glariness (you need to experiment with tips) and the fact that neutral bass and treble isn't for everyone (Precog mentioned lacking resolution, I'd say it's because he's used to heaps of upper treble in most other flagships. My opinion is if that's the price to pay for balanced tonality, so be it; the resolution isn't that bad anyway). Also, while it's a sturdy resin build, it's also a very small company, so it may be difficult if something does go wrong with it.