"I have the HE560 and I could turn the Corda Jazz all the way up on high gain and keep the headphones on my head. It was really loud, too loud to listen to for more than a few minutes... but that shows that I was running out of headroom."
No, it doesn't mean that the JAZZ is running out of steam!!!
It simply means that the maximum gain-factor is medium only. And for good reasons. Lower maximum gain implies less background noises and lower...