While Fiio's X3ii isn't as poorly designed as is the original X3 (which I reviewed here), it still isn't great to use. Seriously, what's with portable hi-fi manufacturers trying to re-tool the classic up-down-left-rigth cross pattern into X, Z, Y, or other unintelligible designs? If you don't agree with me, I have no hope for the mid-range Hi-Fi DAP. However, I reckon that you'll agree with me that the X3ii performs brilliantly. In fact, at least in 16-bit, it even marginally outperforms my favourite DAP, the iPod nano 7G, of which I posted these RMAA results.

The following are the results of Rightmark Audio Analyzer tests.
Source: Fiio X3ii
ADC: Lynx Studio HILO LT-TB
Computer: 2012 27" iMac
Cables: 1,5m Hosa Pro 3,5mm stereo to dual 3-pin XLR (around 8$)

Loads:
NL - no load
SM2 - Earsonics SM2
ES7 - Audio Technica ES7
DT880 - Beyerdynamic DT880/600

Spoiler: this thing is pretty good.

16-bit results summary

24-bit results summary