I currently have Shure SRH840's, using them with a Fiio E11. I plan to keep them for studio music work and practicing bass through, but only five minutes with my friend's Ultrasone Pro 550's showed me how much I'm missing out on with only "flat" headphones.
The Ultrasones were incredible. They were quite open sounding compared to the Shures, certain vocal notes just rung out and created more emphasis and dynamics, and individual parts in songs like We Found Love by Rihanna were more noticeable because the music seemed to be more surrounding. There didn't seem to be a loss of detail or treble extension compared to the Shures.
My Shures now sound compressed and less interesting. I'm looking to spend around $200, and wasn't sure if I should look into anything other than the Pro 550's first. I want the detail and treble extension of the SRH840's, but also having the bass and soundstage that the Pro 550's exposed me to. My main genres these days are progressive metal like Dream Theater, and electro/house/electronic music like Daft Punk and Bassnectar, but I also listen to a wide variety of other genres like jazz and country.
The other headphones I've come across are Sennheiser HD598's, and Ultrasone Pro 750's. I don't know much of the differences or if they'd be what I'm looking for, but I've read the HD598's aren't as full in bass for electronic stuff.