The ATH-M50x are great sounding headphones with a sound that may fall in the neutral category, but with very slight boosts to the bass and highs; a slightly V-shaped sound. The bass is full and has a lot of power. The sub bass has a hint of elevation though, which can make the bass sound a bit loo...
Depending on which model is purchased (16/80/250-ohm), your system may have trouble powering them to get a full sound and comfortable volume. 16/80-ohm should work fine in most systems. If not, you may need an external amplifier.
Despite being sub $100, the MDR 7506 can compete against headphones up to twice the price. These are great if you are just starting to get serious about your audio and you want a relatively inexpensive yet quality purchase.
Due to how accurate sounding these are, you will be able to hear minute details from the sound, including hiss, distortion, and the like. To get the most out of these headphones for music enjoyment, you will want to have a great audio source.