My Grado SR60s have been a constant companion for many years now. After trying many different pads, the big yellow Sennheisser HD414 pad has made them comfy enough to sit on my head for anywhere from 4-10 hours a day, 5 days a week.
However, I recently got a pair of Klipsch X10i phones, which have delighted me with their light and airy soundstage. This has highlighted one feature of the Grados that's previously bugged med. They've often felt a bit too "womblike", sort of deep and moody. So I'm looking to upgrade! Budget isn't unlimited, but I'll consider anything up to around £300.
As previously mentioned, an wide, airy soundstage is preferable. As I'll be using these all day, comfort is a premium, as is a low level of fatigue. Isolation isn't an issue, as I work from home most of the time. I'm also in the UK, if that influences any suggestions.