I finally gave it a listen, so here are some first impressions.
I'll definitely need time to adjust to the button placement. Build quality is solid and I really like the form factor. And also, it sounds good.
The bass has big impact and seems to extend pretty well but in line with the overall presentation is a touch soft. The mids are sweet and inviting with a slightly warmish tone. They are actually pretty detailed but x3 presents the details in a more polite fashion. This can make it sound less resolving next to some other DAPs but the details are there just not as crisply presented because x3's note edges are a bit smoothed over. The treble extends well and again is smooth and on the polite side but has enough energy to keep things engaging but without harshness and fatigue. X3 is somewhat similar to x2 with a spacious warmish but slightly dry presentation, which makes it sound musical but without much warmth taking the spaces between the instruments and affecting the clarity. The positioning is pretty good but x3 lacks the separation of some tighter and more technical DAPs. The layering is great IMO, especially given x3's presentation.
Overall, it's quite musical with a warmish and smooth sound. It might not be as tight and crisp as other DAPs but instead it provides a more polite take on your music without sacrificing too much of the technical performance.