Edited by domin8r20 - 1/27/14 at 6:42am
For portable audio, chances are you would use the FiiO E11 headphone amplifier.
For a Win PC or Mac computer (or, laptop, note book, etc), Fiio E7/E07K DAC/Head amp.
Is there a reason for this other than the optical features? I went with the E07K because I didn't see using optical sources.