ODAC/O² Easily
More seriously @
sonic2911
ODAC/O² separetely = > "transportable setup" , no drivers , ODAC is USB powered , and O² has is inbuilt battery , if a part fail you still have the DAC or amp working . ODAC/O² Combo drivers less, and the most compact of the lot .
Schiit Combos => Great Looking (well subjective ) , more power for some hungry planars , as for ODAC/O² separetely if a part fail you still have the other , spdif inputs and preamp ...
A-GD => even more power than Schiit offering , preamp function , spdif input as well , and a all in one solution if you prefer this kind of way .
(As for power requirement for planar i think that O² is fine with most of them
) .