whats the sound difference between the k518 and the sennheiser hd25-1-ii? Is it more than worth the sound difference, and would it be readily noticable with  my mp3 player?

The seinheiser hd25-1-ii seem too expensive for me at the moment, for that money I would prefer to buy headphones for indoors/airplane travel, not everyday use.   The k518dj seem good, I am concerned about whether they would comfortable on the ears, my journey into work is over an hour long...

I'm looking for a pair of headphones for use with my sansa clip mp3, to and from work on the bus and walking(I'm in the uk so they really shouldn't break at the first sight of rain), which can then be placed in my bag throughout the day. So it they should preferably have very little sound...