I was doing some listening with my HD650 and the 2Move set to high gain, and I forgot to change it back when I went for the TF 10 Pros( you have to open the amp to change the gain ).
I haven't done A/B on them yet, but with high gain the airness was so much bigger and better, the bass was so much tighter and deeper, but after a while the sound started to irritate and was kinda harsh to my ears. And, of course, it was very hard to set the volume to a nice level. Before that, I was always using low gain with my IEMs.