That would be the HD 700. I have both and the 700 is better in every way, except the 560s has better sub bass. That being said, the 560s are surprisingly close to the 700 and apparently the 660s uses the same drivers as the 700. I think you should try the 660s in person before committing.

EDIT: Forgot to mention that the HD 700 are discontinued unfortunately. The 660s are similar but idk if the soundstage is similar as well. In that case, the HD 800s would be better for you, if soundstage is a priority.