It depends what you are using it for and what you choose to pair it with.
There are eight! different versions of the Hifi-m8.
see the first page of the impressions thread
I use an ipod touch 64GB with mine(I use FLAC on flacplayer app). Some would prefer the ipod classic due to the amount of GB space avaliable.
I myself choose the idevice version backplate,
with Unbalanced: 1/4″ jack, 1/8″ jack and Balanced 4-Pin XLR jack -frontplate.