TheDreamthinker
Headphoneus Supremus
If you didn't like the sound signature of the other Fiio DAPs, then unfortunately I don't think you would like the X7 either. They all do share a similar sound.
And I have to admit that when paired with my ER4S, the X7 does get a bit too bright for me. It's not to the point of being unlistenable, but it is somewhat annoying. Otherwise, I thought the X7 drove the ER4S well - plenty of power for the IEM, and created a pretty 3D soundstage (well, as 3D as it gets on the Etymotic IEM).
To me, on initial impression, all the Fiio DAPs i tried felt splashy and aggressive (not in a good way), to the extent that it lacked separation.
Although I am generally on the look-out for more aggressive soundsigs (as with the ER4s), the Fiio overdid it for me.