here is a sound comparison on how the m50x sounds compared to another popular choice the dt770
https/www.youtube.com/watch?v=4pK7QbLNjno
i personally use the ath-m50s which is the original model (the m50x is the newer model with a modular cable) and they have worked great. personally i dont feel like they have too much bass and i wouldnt call them bass heavy however they do have more bass than some other models you can compare them with.
i've used them for mostly music and movies but i have done a little bit of gaming with them and they sound fine to me. some say they have a narrow soundstage (the term used to describe how 3d the audio sounds to you) however this is common for closed headphones and honestly is a very hotly debated term. some say the dt770 has a wider soundstage (and it might) however all of the headphones listed as a good soundstage are all open or semi-open designs (headphones where everyone can hear what you are listening to and you can hear everything around you) so it kind of defeats the purpose of headphones right? personally i dont have any issues with the set for sound quality considering the great price (if in usa you can get a pair for $99 ath-m50s open box but brand new) and even the full retail of the m50x isnt terrible (but you can find it on sale for cheaper too)
since they are only 38ohm they drive fine from laptop/pc headphone jacks, ipods and cell phone headphone jacks. i've traveled often with them and i've never had a device they didnt work with. you do not need to buy a soundcard to power them however if your onboard sound is complete junk and you get static, distortion, hissing or other bad audio effects then adding a soundcard (or buying an external soundcard or external DAC) is suggested to fix the issue.
the m50 design is pretty hefty and stands up to daily travel well. its also folding which makes it very compact. as long as you take the time to fold them up, wrap the cable up and put them in the bag (or hang them up on a headphone rack where they cannot fall) they will last you for years. my pair is about 3-4 years old now and still going strong. if the earmuffs start getting hard/cracking/wearing (common for many headphone sets that get lots of use) you can buy replacement pads for pretty cheap as well.
TLDR: great set. an alternative would be the dt770
note about dt770:
while it compares favorably with the m50 it has been noted that the 250ohm (one which requires an amp) sounded much better than the 32/80 ohm models. of course an amp isnt really a nice option for travel unless its at an office desk where you have ac power. the design also isnt folding. i'm not saying the 32ohm version is bad just noting what i've heard from consumers.