Here's the thing - I've been playing around with FiiO E11s power output switch (under the battery), and with the headphones I use, I don't really hear any difference between low/high power (maybe a slight one, but I'm thinking it's just my brain telling that it should work better on high). I use MBP -> FiiO E11 -> Koss Pro DJ100.
So the question is - are the DJ100s easy enough to power so that there might not be any difference? And what parameters should I be looking at for heaphones to get the idea, when they would benefit from a high output power (e.g. impedance, or something else)?