Glad you found a headphone that worked out for you.
I've owned the HE-400 as well as the DT-990. I guess it doesn't matter for you now, but for other people reading this thread and trying to decide between the two, my basic opinion is that the two are fairly similar in general signature (both have emphasis on bass and treble) and that the HE-400 is significantly better-- the DT-990 will give you slightly more bass quantity (not quality) than the HE-400 as well as slightly more natural mids. For everything else (most notably, bass slam, bass texture, bass extension, overall detail, layering, imaging, and speed), the HE-400 walks all over the DT-990. Non-sonically, the HE-400 is also around twice as heavy as the DT-990. I found the HE-400 perfectly comfortable but it is a major problem for some people.