tomscy2000
Headphoneus Supremus
The only thing that bothers me is the low impedance of ax35 (8 ohm) FiiO x3 recommends >16
Haven't had any issues with SQ due to low impedance.
Yep, that's a non-issue.
The X3 has some of the lowest output impedance values for a DAP, amp, etc. around, and it uses a high current-delivery opamp in the AD8397, so there's zero issue. The only thing would be that the X3 drains battery just a little bit quicker with the AX35 (but not much).
Also, keep in mind that the impedance value is only set at where it's tested (1 kHz)... because the AX35 has a BA tweeter, it will reach well above 8 ohms in the upper frequencies.