Audeze LCD-2C is an option. I've owned one for a few days, and I'm happy with it.
Some say the Mr.speakers aeon flow is a good alternative (haven't heard it myself).
I tried the Hifiman edition X v2, which I liked even more than my LCD-2C. Maybe
you could find one used at $750. ZMF headphones I think get quite a bit of praise,
but again, I haven't tried them.
For better staging and imaging, I think Sennheiser HD800S is a good alternative.
But a used pair might cost you a bit more than $750. I think it's more of a neutral
sounding headphone, though. Before I bought the LCD-2C, I used Grado SR325i,
which is quite bright, so I tended to find other headphones dark while they actually
sound neutral.
Visit a hifi-shop if you have the opportunity, and try out a bunch of headphones.
I almost bought a certain headphone about this price range based on others'
opinions - I'm glad I didn't, as it was underwhelming to my ears.