So I was at the NY meet yesterday, and had a chance to listen to X3, X5, and AK100, 120, and 240. This was with UE reference monitors(very neutral, clear and transparent that reveal how well the source is).
Best to not best:
1. AK240 or 120 pretty close
2. AK100
3. X5
4. X3
I was surprised how great sounding AK were. X5 is no slouch as it sounded more musical than X3. Didn't like the X3, X3 has the usual electrical sound that I've experienced with their amps(haven't been a huge fan of Fiio product sounds, always been disappointed, so I started to lose faith. I guess specs is not everything). I say I like the direction Fiio is going with X5, the sound is very musical.