Just like to share what had been said in the Chinese Forum, erji.net:
Apparently James is working remotely from the hospital?
X5 is more neutral and transparent than X3, and the writer of this review believes X5 sounds better than AK120. AK120 seems to be better at 'controlling', however he believes the X5 has 'better' soundstage and better highs, mids, and lows. (I don't know what he means by 'better', and I believe it may be too subjective.)
Few things to note:
1. Requires amping ( the reviewer paired it with E12) to drive 'bigger' heafphones and to gain better 'control'. (This is consistent with what James told us.)
2. The reviewer is an IE800 user and loves Senheisser. He used SE846 and IE800 for comparison and believes X5 performs better on IE800 than BA based phones. (Again, I am not sure about that due to the reviewer's own preference.)
3. James and his team are working tirelessly to make final adjustments.
Please excuse my poor (and not full) translation.
To add on:
1. The reviewer commented that the X5 does a good job with the Sennhiesers (HD650, HD600, HD598) (He notes how close the HD650 sound is to the IE800), ATH-ESW9 and even the Beats headphones (lol @ his comments on how good they are with "black men's rap")
2. You can customise the UI already; the reviewer changed the fonts and the background image in the play screen to prove this.