I think that I'm more looking for something supra-aural- I find full size around the ear headphones rather uncomfortable. I wear glasses and whenever I wear those 'phones it feels really heavy on my head and my ears do feel quite cramped.. I tried a Audio Technica full size headphone @ a store and they were quite uncomfortable (I don't remember the model, but they do look like M50's). Are the 518's similar in terms of comfort or are they rather different?
EDIT: I live in Hong Kong so I have fantastic shops to go find IEMs/Headphones ^.^ The guys at the store do recommend 'phones to me but I wanted a second opinion from headfi before making my decision.
I find the 518 to be comfortable (it's big bro the 556 & 598 are more comfortable. However, I also find the that the M50 is comfortable. On these issues only you, wearing these cans for the duration of your listening sessions will be able to tell if they are comfortable for your head and sensitivities.