I'm not sure why people dismiss the Beyer's without having listened to them.
I have the DT 770 Pro80's, and they are real easy to drive. I occasionally use them with my ipod nano, and the sound is just fine.
Even the Beyer website says that the 32Ω and 80Ω version are made for portable devices.
The 770's have fantastic bass, are extremely comfy, and are a great closed set of cans.
They are pretty easy to find as well (amazon?).
When I was deciding on a closed set, I actually auditioned the Shure SRH840 & Audio Technica M50 (among others), and my deciding factor came down to comfort.
Personally, I didn't like the 840 sound. The M50's sounded great (and even made the Beyer's sound thin in comparison), but the DT770's comfort was just outstanding
(which is a big deal for me because I wear them for hours on end). I have since bought the M50's as a portable set, but always reach for the Beyers at home when I want closed headphones.
edit: the M50's are definately U shaped to my ears. And the DT770's have better isolation.
Edited by Bee inthe Attic - 2/4/12 at 5:18pm