You're probably not going to like this but here goes anyway.
I listen to a lot of piano and recently auditioned new cans for with a view to replacing my HD280s. This included the HD380s. They sounded great with rock and similar genres and the bass was a great improvement on the 280s but when I auditioned using piano as my source I was disappointed. These cans changed the sound of the piano so it no longer sounded natural and I decided I couldn't live with a piano sound like that. It had a similar effect on string tones.
So I'm guessing that you are EQing thes HP because of this sound signature?
Anyway, to cut a long story short I parted with a bit more money and bought the Shure SRH840s. I've now got the 280s at work running through a small amp (PA2V2) and they are a great sounding set of phones, they just need to be driven to get the best out of them. That said they are not a patch on the Shures.