You need a headphone amp for this headphone to sound good. I bought one recently. I also have a Beyer DT990Pro headphone. The Beyer is an open back type and the M50x is a closed back. The Beyer sounds more open . However the M50x has tremendous punch in the bass notes. Does not go any deeper than the Beyer but is punchier and does feel closed in like most closed back headphones.
The Beyer is lighter and possibly more accurate but the M50x is more dynamic sounding and great for lively punchy music. Suggest you try it with a headphone amp , not with the minuscule output of small devices. Plugging it into a receiver socket isn't good enough ( as they have internal series resistors). You need a dedicated headphone amp , or build one ( JLH for example!).
Headphone amps are another whole ball game. There are fans and addicts in the headphone arena with several web sites dedicated to them. Try
http://www.head-fi.org/ and
Headfonia Headphone Reviews ,
Headphones - Top Resource Sites and Headwize.com unfortunately doesn't work anymore. But the pages are archived. Check out:
A Quick Guide To Headphones | HeadWize
Some of it is sheer insanity !
I did toy with the idea of dumping the M50x but after listening for a few days I think I'll keep it. It's far more punchy than the Beyer and for some types of music it's great.