High-end Sennheiser close to HD598

[cossix]

I have the HD598 and just bought the HD650. After burning the 650's in (and stretching them a bit for that matter), I am starting to wish I had purchased something a bit faster and clearer in the treble. Back to back, the HD598 has much clearer highs and is more fun for songs that already have no bass. Going off of my enjoyment of the 598 signature, would you recommend the HD600 or 700? I have heard the 6xx series are pretty close together and owning both may not be worth it. If I want clarity and tight bass do you then think the 700 is the way to go?
 
DSD64>Schiit Modi 2 Uber > Magni 2> HD598,HD650