Claritas, these are 250ohm, not 600 ohm. I too didn't expect this, but unless you're listening at insane levels, they actually sound pretty good through the Air's headphone out. 95% of classical music works well: the volume levels are too low for the remainder 5%, but this can be fixed with a 2 notch bump on the db levels through the iTunes EQ. All of pop-rock sounds adequately loud. Do try them out with a Macbook Air at an Apple Store near you.
Of course, they do improve with a good dac / amp but that's the case with all headphones.
About the "fabled brightness", I too have heard it on a few pop/rock recordings. But on classical, never. And I almost did not buy these headphones because I'm particularly sensitive to sharpness in the highs. Thankfully a friend insisted I took a pair home overnight for a listen.
Edited by stevej12 - 4/5/14 at 11:20pm