The problem with these kinds of phones is that they're too efficient, too sensitive, too powerful, too low impedance (or too wildly varying impedance over the frequency range) for most MP3 players' amps. And it seems the crossovers in those multi-armature designs make matters even more complicated.
There's a usually rather broad sweet spot where phones work well with MP3 players, but same as on the opposite end of the spectrum where you have 300 Ohm Sennheisers, or 600 Ohm Beyers, those (in reality, depending on frequency) 8(!)-20 Ohm IEMs with a sensitivity of sometimes over 120dB/mW don't work well with most MP3 players.
For example, the SE530 are especially bad when it comes to hiss: they hiss like mad with about anything - also with many fancy, high-priced headphone amps. I only know two, the Arrow and the Headsix, that don't hiss with the SE530. Another problem is that such IEM's low varying impedance affects stereo crosstalk (soundstage) and bass response (roll-off) in a negative way.
Basically, those "high end" IEMs need more issues "fixed" than some beefy full-sized phones in a portable rig. My HD650 only need to get louder and more dynamic to make them enjoyable, they don't have the issues that plagues my IEMs.
So yeah, to answer your question, the Arrow definitely improves listening satisfaction with those kinds of IEMs a lot.
