i've been using a pair of ath-m50s for at least 3 years now and i will never go back to anything less than another pair of studio headphones. the difference between studio headphones (and i'm talking real studio headphones not complete junk like beats by dr dre, sony xb or bose) is really quite large. in fact i cant listen to low quality music anymore because i can actually hear the flaws while before i did not hear anything wrong. music also sounds so much better and listening to all your songs again is a real treat since they all sound so much better.
with that said, the ath-m50x is a new version which has a removeable cable and they give you 3 types of cables to use. the older m50 (coiled cable) and m50s (straight long cable) however are available for as cheap as $99 brand new but open box on ebay at times.
the only thing some people say about the m50s is that they dont have a wide soundstage however i can say from using them for a long time that this hasnt been an issue for me at all and that they sound perfectly fine. an alternative to the m50s would be the beyerdynamic dt770. the 250ohm models sound the best (in the dt770) but need an amplifier to run. the 32 ohm model (and 38 ohm m50 since they only come in one rating) do not require any amp and run fine on portable devices including phones and ipods as well as on your computer.
if you care you can see a photo of the m50s in my signature link.
here is a comparison of the m50x wit the dt770
https/www.youtube.com/watch?v=4pK7QbLNjno