I'm a Chinese college student,I only speak a little English.But I will give you a good news with my little English.
At 22,Fiio says X3 will with USB DAC,Today I had the opportunity to participate in beta testing on my laptop with windows 8 etp.
Fiio give us a new firmware with DAC mode and a drive.But Mac users do not need to drive.
I spent the whole afternoon with my laptop and X3,also ATH-M50.Now,they work very well.
I have no permissions to upload my Image,but soon after you can do the same with your own X3.
Are you expecting that?