Summary: The sound of the MS400 is marginally better than the MS300, with better bass and a less colored midrange, but the highs are still softer than headphones like the v-moda M80 and Senn Momentum, which are already soft by hi-fi standards.
Summary: I really wanted to like these MS400's as they were very very comfortable but compared to the similarly priced V-MODA M80's the bass sucks and the highs are overly harsh. I did enjoy the spacious soundstage that they created and if it weren't for the lack of bass I'd have been tempted to keep them...
Pros: Very comfortable circumaural headphones. Somewhat flashy (could be a con) Carbon fiber earcups Creates a nice soundstage, sounds very "open" Highs are bright, if that's your thing...it's not mine
Cons: While comfortable the cloth covered grill that protects the drivers did push against my ears and caused some discomfort after listening for a while (more than 30 minutes). Feel cheaply made, plenty of plastic. Very weak bass response save for upper bass (70-80Hz+).