That's what I feel is lacking as well. Screams sound... well.. a bit dull. Guitars sound thick and more chrunched than distorted. Don't get me wrong, they're still good. It's just that they lack the bite and aggression. Do you have any meelec balanced tips around? They do however lessen the mid/upper bass and take away some of the warm character but to my ears they bring out the upper mids better because of that. I realised that I like those tips with all 3 of my most used iems (ASG-2, UE900 and FA-4E). If you live in EU it would be quite easy for you to try out the Fischer Amps FA-4E Xb. I just can't stop recommending them as an upgrade from UE900. With meelec balanced, a lot clearer, less mid bass, about the same or more sub bass, better impact, more extended treble. Just overall better in my opinion. And they are scary when it comes to screams. Coupled with a source with clear, slightly forward upper mids it's a delight to listen to them. I'm not trying to bash the UE900, I love them. It's just so damn hard to think of a reason to put them in my ears these days when I have something that's so similar, only better for my preferred sound signature.