The first line was not directed at anyone here but at the fact that I couldn't even link to a HeadRoom graph (which now has shown up...).  My apologies if it came across otherwise.  Now, I can't really tell if you are being serious or sarcastic... one of those cases where I'm missing the...

The M50 certainly does have a much more stable impedance than the HD280 Pro (just grabbed something to compare). Is this the basis for stating that the OP would not hear much benefit with an amp? Do we have a reference for the output impedance curve of the 'iPhone'? I have only seen nominal...

I have no personal knowledge but this post refers to a 7 millisecond delay (0.007 seconds) not 7 tenths. http://www.head-fi.org/t/587912/fiio-e17-alpen-first-impression-final-thought#post_8013926

In some cases, 100% is bad. For example, with a 0db disc my head unit starts clipping when you pass 30 out of 35. Why would they do this? Because most recordings don't reach 0db and many don't get close (at least for much of the recording) so you need to be able to turn the volume up to maintain...

As mentioned before, it isn't necessarily a matter of the amp amplifying. Rather it is an issue of impedance interactions. Because getting a low output impedance tends to be more expensive (and not just in dollars) mass market sources will tend to have higher impedances than dedicated 'amps'...

Nearly 10 years ago I got a deal on a set of Shure E2 (I think that's the right one) and while I know they are bottom-end canalphones, they satisfy my fairly inexperienced ears (more experienced with home and car audio, but still mostly just picky rather than actually experienced).  That said, I...