A) might not just be your thing, B) the jump might be so big you need time to understand the differences (like jumping from MoonDrop waifus to appreciating the masterpieces of impressionist art), C) the M50x's are laser sharp in the treble and have overdone porridge bass so your ears might be fucked like mine were after using them for a few years that something balanced sounded boring (HD650 for me) and it will take time to readjust, but the M50x's will likely sound horrific afterwards.

The amp is likely fine. An iBasso DC05 or Apple dongle is. I recommend EQ (Oratory1990 preset) to bring the bass up a bit. They're really damn nice headphones for most people. The big soundstage also makes them more diffuse sounding in the bass especially which is a bit less gripping and more ethereal than you're likely used to.