What is the next step from HD 560s?

I've tried at least 10 pairs of headphones over the last two years. While the 560s isn't perfect, none of them in the under $350 range have compared. Even the HD6XX that people love, it just sounded crushed and like the sound was at one point in my face/head.

Every time I listen to the 560s I am blown away by the detail, soundstage, imaging, wide sound, vertical and horizontal, and just total goosebumps. Moreso, just the detail and separation is incredible. I can hear each individual instrument, where and how they are recorded, etc.

So... what is the next step? I wouldn't mind a TINY bit more warmth and less harshness/fatigue. But I don't want to lose the detail, soundstage, separation, etc.

Opinions? HD660S?