Summary: For a portable, the ES-10 has surprisingly substantial sub-bass--very similar to the M50, with both able to almost match the D7000 all the way down to 30Hz (although the D7000 does it effortlessly, while the two AT models struggle a little bit more). In fact. The ES-10 and the M50 sounded so similar to the point where I wondered if they use the same driver. It's a pleasant and warm sound without any sibilance, but not as articulate or airy as I'd like.
Pros: Warm and balanced sound, authoritative bass extension and weight, non-fatiguing