So here's where I'm at. I own Denon AHD2000, Fidelio X1 , Grado SR325 ( modded with maho shells and recable) and Senn. Momentums. I think I've got the Mid-Fi bases covered and prefer a somewhat colored sound with good detail retrieval>Soundstage>comfort. I generally prefer a somewhat colored headphone and lean toward the sound profile of the Denons but would prefer a tighter lowend with more detail, the highend doesn't bother me. The SR325i are a bit harsh but otherwise pretty good sounding.
I like rock and metal. I know that soundstage is kind of a non-entity when it comes to recordings but prefer a headphone that has a quick response and no blurring in the low end. I do also like live jazz, vocal and some classical music. The Shure SE535Ltd do these genres quite well while sacrificing soundstage.
I've come down to the Sennheiser HD700 as a bridge between the lauded HD600 and HD800. The HE500, I'm afraid would be a bit neutral and boring ( laid back ) for what I like although they get rave reviews for the <$1000 crowd. The AKG K712 Pros seem to be a good all around reference headphone with a bit of a bass bump and good extension. The AKG 712 and HD700 would have that immediacy and aggression I crave but the HE500 seem to good to overlook.
If I could save a bit-o-cash on a HD700 alternative I could probably buy a decent amp. Currently rocking the Fiio E17 and Fiio E9c