is there really a big difference if your earphones' impedance is 16 or 32? is 16 significantly better?

the impedence is just a measurement in how much resistance there is between the signal you're listening to and the sound thats actually getting to your ears. the lower the ohms, the more powerful a sound you're going to get, and it will sound different. most people can kinda hear the difference and say "yeah, it seems stronger", but cant hear much beyond that.

frequency response will have more to do with how all the highs, lows, mids, etc. will sound in relation to each other and the recording your listening to. think of it like the radio in the car, wouldnt it suck to only have a "treble" knob, or only a "bass" knob? well, same thing here, you want to cover the whole spectrum, and make sure that each part of it comes out nice and full.

as far as the voice coils thing, i'm not as sure with that one. by the time i got that far, i was already trying out 3 sets of headphones and i already could tell which one i liked for the money.

end of the day, when you start to pay more than $100 for headphones, i'm sure you'll be pretty happy with whatever you get. most people cant really hear the difference in a lot of things anyways.