The main problem with iGrado is they were made cheaply, maybe too cheaply. The headband was initially really really uncomfortable, pinching my ears pretty bad, it became unbearable after 30 minutes. Took a lot of plastic trimming to make it acceptably comfortable. They really should have used a better headband design to start with.
The mods been done to mine:
*openning in the front foam cover (similar to the quarter mod). The stock iGrado without this mod do sound muffled.
*Taking out the foam pads behind the drivers. Not sure if it made the phones more airy, but if you read my last post in this thread, you should understand why I did that.
* Recabling. I didn't use any audiophile grade cables, just recabled to a thicker, longer, more robust cable. I used the cable from my Sony CDV-180, which, internally(copper strands) is similar to the stock iGrado cable, maybe just a hair thicker (not sure), but the thicker outter skin/insulation/protection makes the Sony cable about twice as thick externally. Electrically the Sony cable is probably not of any higher grade, then why would I want to recable to that? well I use the iGrado for my guitar amp, I really do Need longer and more robust cables, the stock cable is too fragile for guitar use...
I'd say my iGrado, with the quarter mod done, have sound quality comparable to my sportapros. That is if sporta perform normally. Sportapro sometime have resonate noise when playing certain music, probably due to the cheap housing. Yes, I have noticed that quite a few times. iGrado's don't have that problem, but the sound is more flat (or you can call it smoother?), more lay-back, and, to my ears, less fun than the Koss.
Still, they are not bad phones for the price.