Hmmm I am suprised because after you hear something with textured bass, open soundstage, non recessed midrange, non sibilant spitty vocals, non boxed in sound then the M50 sound a bit mediocre.... They do have a decent sound and a good FR out of the box and they are also quite exciting to listen to but they are not very refined at all compared to better headphones.
You do realise that you are comparing the M50s with something costing much more? I had the M50s for a period of time and I thought they were pretty decent for the price and features wise for a full sized portable headphone, they are/were pretty much the best out there. I would not hesitate springing for them a second time if I find one cheap.