I bought these on a whim and have no regrets. Just let me say wow, I'm just hoping when I get my he-400's they don't get overshadowed. But the ue900's are going to be for work and on the go. I've only had them for less than a day. I've just loved them unequalized, they are the first headphone/iem's that I liked unequalized. So they will need a bit more scrutiny when I get my he-400's but apples vs oranges really. If anyone has a recommendations for a portable amp that could tackle both? Pm me thanks and to anyone pondering the purchase, if you can...