It has only digital inputs and can't work as headphone amp for separate analog source.
..And neither does Fiio E10K have analog input.
Yep. If the OP does need an analogue input for the headphone amp, then the E10K and X6 aren't much use.
I'd missed the idea was to use the headphone amp with the TV/humax box. Completely rules out the E10K anyway.
Doesn't either TV or Humax box have optical output?
X6 would work quite well if there is optical from the TV or box and use the USB for PC. or coaxial from the Humax, if it has it.