I find my Vita to be quite dark sounding, much darker than any of my other sources. Sounds too soft and muddy. I really dislike it as a DAP and would never pick it over my others. In fact, it even bothers me sometimes when playing games.
I seem to recall people putting some stuffing under the pads to lift them up a bit more. Since amplification has been coming up again, the Z1000s run great with portable devices but I find they really scale well with better equipment.