I've done some extensive testing with the X1 vs the X1 + E11K, and I personally find myself preferring the latter pairing.
The X1 by itself seems to be relatively more squashed towards the centre, the conventional Fiio sound (I do use the word relative, because the X3 is even more so IMO). The X1 standalone also sounds slightly more forward in its presentation.
The X1 + E11K is more expansive imo. Stereo separation and soundstage as a result become slightly better. The presentation also becomes slightly more laid back. I also find it to be slightly more resolving.
I must say though, the Kogan MP4 player is more detailed than either setups, but also thinner sounding, less refined, and lacking in the low frequencies. It is also, of course, less than half the cost of the X1 by itself, and purely with regards to SQ, is the ultimate bang for buck player.
But when you add in UI and build quality, the X1 is equally good value IMO.