The Simgot EM6L are quite frankly the best thing I've ever heard. They have some of the smoothest treble of any IEM regardless of price and are tuned extremely well for a fun, dynamic, V-shaped sound.
The Simgot EM6L has a few advantages over the Beyerdynamic DT990 Pro 250 Ohm. For one, it has more sub bass, smoother treble, and it isolates the sound. Although the Simgot EM6L lacks some musical sparkle in the highs, it has a more polished sound as if you were in a somewhat dampened room...