It's funny that you ask. I think the HP-2's are like a closed back set of Grado's. They have as much mid and upper detail as my GH2's and, like the GH2's, I felt that they were a bit bass light. I think the imaging and separation was maybe even better than my Grado's.
However I couldn't get past the fact that I was buying a set of closed backs to bring the bass.
I really liked the HP-2's, but I prefer the Focal Elex's/Clear's, Grado GH2's, HE6se V2's and even the Basso SR2's.
And I found my closed backs for the bass.