Well the 598's are out I think, they cost around £200 unless you can get a set second hand or something.
The AD700's are lacking in bass, but have amazing an amazing soundstage. Do you like bass? If not then these might be good for you.
Another option are the Beyerdynamic DT 990 pro headphones. Good bass, with good soundstage.
There are some other headphones as well that you might consider. The Fostex T50RP, can be modded to sound way better then their pricepoint. Not sure how you feel about doing some DIY stuff.
The Sennheiser HD 558's might be worth a go. And a set that I think could be worth a listen to are the Creative Aurvana Live, a good all rounder and a good price.
LAstly, I will recommend my own headphones, the JVC RX900's can be modded too and they are really good value for money.
Sorry, for the vague answers, just a little tired. I am sure other people like Marsman and Phal might chip in.