I just watched this video where he reviews just about every common interface. https://www.youtube.com/watch?v=gMuA-2FbJxE Right at the end he does a real quick overview of each. He got to the Motu M2 and rated it at the bottom of the pile. His claim was the headphone seemed to introduce distortion into the recording when turned up? Weird.  Now I've always had trouble with my M4 since the day I got it 2 years ago. Randomly it would record audio distorted. A total system re boot fixed it