I'm not sure this has been brought up, but I think it would be nice if Fiio concentrated some effort into reducing the jitter on the X5. The jitter numbers on the X3 are startling to say the least. I don't expect AK120 type of performance but something closer to the AK100 would be nice.
None of the X3 reviewers including me had any actual problem with jitter through coaxial out.
Jitter is extremely over rated in the audio world. If you re read every post about jitter in the X3 thread, you should have a good idea about it.
If we can't hear it, and don't note it, and the jitter numbers are beneath human hearing, does it still matter to you?