+1 for burning in these headphones for a week or so. It seemed to improve the treble performance for mine in particular. I used the track here to burn mine: http://www.jlabaudio.com/burn.php

I've never heard the 780's but I've had my HFI-580's for about a year now and I completely recommend them. They were a little clampy on my head at first but they loosened up and the sound is really fun and rich. The soundstage seems pretty wide to my rather novice ears (this is my first set of...