ooh, a M50 thread
I'd like to add my input on the M50:
I've owned this for a few years, the straight cable version. They along with the AD700 was my first step into audiophilia. I've bought other headphones after I began the hobby.
They have a bassy, yet clean sound. Most of my friends, if not all whom I've shown my headphone collection prefer the M50 (even over the HD800), as it has a clean sound while being bassy and it works for most modern pop music, rnb, hip-hop, etc.
Coming from iPod earbuds, these were like heaven. However, I've been growing old of them, and I'm rarely using them these days, they do have their disadvantages; soundstage comes to mind. I am thinking about selling them sadly. But they're not overrated, but I think these are one of the best pair of headphones one can use as a step into audiophilia.
EDIT: I think they sound good from an iPhone, but we all have different opinions. It does sound far better with amp + dac.
EDIT2: I'd like to add that the M50 outclasses the SR80i in almost every comparison; detail, soundstage, enjoyment. I use the Grados for rock/hard rock/blues/metal that has a strong emphasis on the guitar, they give a unique colored sound. But the M50 isn't bad on the aforementioned genres.