Ok I just bought a fiio e10k since these can ship faster. Plus I don't see myself using my athm50 or x2 outside of the house.
I have read the previous comments from you not being too happy with your X2 purchase.
I would like to add the following:
I am sure, an amp will improve the sound. But X2 is very 'Hi-Fi' sounding straight out of almost any source.
I do not own the m50, but I do own a M-100. Bass is slightly more enjoyable on the M-100. But in everything else X2 just spanks the M-100. (Mids, highs, space, naturalness, balance, imaging, etc. ALL the rest.) And being in this hobby for more and more years teaches me bass is just one of all the mentioned aspects of overall listening experience. (I still love bass, that is why I have got X2 and M-100, not K702 and SRH940 for instance. But bass is just one of the many amazing attributes of sound.) And X2 gives you more access to all of it it than m50 or M-100.
(Might worth to mention, that most of the reviews prefer M-100 over m50 in overall sound quality.)
So my advice would be to be patient, and give it some time. The amp will be an improvement, but not the clue of understanding X2 (or opened Hi-Fi headphone sound in general.) You have to get the taste of it. Like no child was ever born loving blue cheese or beer or islay single malt whiskey. But as we spend more time with experiencing the world, we discover the joy in less known, less popular tastes, activities, experiences. This is called the refinement process of our taste.
X2, and most of the opened back Hi-Fi cans are not just one, but many steps further from the m50. (Or from any closed cans.)
They are a different world.
You might have expected fireworks and candies from X2.
Instead of sinking into this disappointment I would suggest to sink into the details of sound what X2 provides.
I would suggest to give it a few days, and than report back please.