My wife uses the CX300 and likes them a lot. We are still a mixed house with the rest of us still using MX400. Nobody would claim the MX400 is the greatest, but it is a clear improvement over typical so I recommend them as a good reference set. Your ears need to unlearn the distortions cheap headphones use to sound louder, punchier or whatever before you can appreciate good clean sound.
Good sound, especially bass has a lot to do with how it fits in your ear, and that will vary from person to person.