The spec is unimportant. Your digital files have nothing over 20Khz and it wouldn't matter if they did.
Here's another review. http://www.headfonia.com/fiios-power-pack-the-fiio-e12-mont-blanc/
Interesting review, it seems that only good pairing is with HE400 and some bassier protable headphones and doesnt work well with iems. Anyone else agree with this?