Hey all. Long time browser of this forum, equal time troublemaker. I am no better versed in the way of the amp and speaker than any hobbyist who likes to read. But you change up the technology a bit and I feel totally unqualified to comment. Say you have an Ipod or other mp3 player, you hook headphones to it. Aren't the same laws applied to mini-device/headphones as amps/speakers? You still have an amp, pushing sound through speakers, only smaller. Is this correct? The Ipod for instance, must have an amplifier in it, because it has its own volume control and power un-powered headphones. Wouldn't users of an expensive mp3 player really want to know the impedance of the speakers they're hooking up? Is there a potential to blow the player if you just jury rigged a pair of speakers to the headphone jack? Now from what I've been reading on msg boards the Achilles heel of the Ipod is the battery since they're built in they're not easily replaced. Keeping the lifespan of the battery up, using fewer precious recharge cycles is important to users. Wouldn't the headphones you're using be paramount to this? Wouldn't the consumer be interested in efficiency ratings of their headphones? What about their impedance? Wouldn't Ipods have recommended impedance for headphones? Sorry if this post doesn't quite fit the recievers board. Upon second look I stand behind my initial impulse to post this line of questioning here.