Beyond the classic HD650...?

I absoutely love my recently acquired HD650 headphones, for listening mainly to classical music. They are currently through a Fiio K7 (and waiting for a balanced cable).

My innocent (and ignorant?) question is this. Could it be even better?

I read about the soundstage thing and want to know how much I am missing. Should I start saving for HD800S or a planar magnetic or whatever?

I am worried that, for a lot of extra money, I may be underwhelmed. Or worse, I might even find the brightness, precision, spatial thing a bit distracting. I am not a gamer; and I will never need whatever it is that sound engineers and mixers talk about.