Thank you, everyone, for your helpful replies, I really appreciate your opinions. I am a lurker on this site, but I've spent many an hour browsing the forums. MalVeaux, I've read many of your posts on here and respect your opinion, so I have noted all your suggestions. I am aware of all the cans you listed, except the AD2000, MA900 and the Mad Dogs. It's such a personal and subjective thing, this headphone malarkey and just over the last couple of days, between the madness of my gigs and school Christmas concerts, I have been giving the HD598s and really good listen at night when back at home. My mind is changing again as they have, on a few occasions just recently, impressed me so much that I've felt guilty about writing my original post. Just shuffling my hard drives music folder, things that have stood out have been tracks from Pink Floyd, Jeff Wayne's War of the Worlds, many intimate acoustic/vocal things, solo piano and even an old Public Enemy tune, where the extension of the bass pleasantly surprised me!
I have noticed that, contrary to others opinions, I believe that these cans are not very forgiving of lesser quality mp3s. This is surely the sign of a good headphone, if accurate reproduction is important to you? Also, I got my twin brother to try a few things out, music and films clips. He is not an audiophile, but he has a great ear and is neither easily impressed or disappointed regarding sound quality. He loves music before sound quality. His unanimous reaction to nearly everything I played was that they were amazing cans. He thought they were a bit bright, but the lack of bass kick emphasised that too. He said he hadn't heard detail like that before though in headphones and pointed out that he'd never realised a particular vocal was doubled before in a track he knows really well.
Still, I have to make my own mind up about this, but I'm definitely feeling somewhat emotionally connected to these now. Plus, they are so comfortable and look like they mean business!
Not being disparaging to anyone on here in particular, but I have found it quite disappointing reading threads here on a few occasions, where the contributors have 1000s of posts and are Headphoneus Supremus status, discussing a high end set of cans, then posting some YouTube or SoundCloud ****ty sounding track of electronic/ambient/trance music for a real test of the cans. I realise then, that what I want out of my headphone choices are in a different ballpark. Electronically produced music can certainly test dynamic range, frequency response, imaging and all those other technical aspects of sound reproduction, but as an orchestral trumpeter who is attuned to what sounds realistic and lifelike, I have a need to accurately hear the overtones and harmonics of a sound reproduced as faithfully and evenly as possible so that sound is convincing and not artificial. Of course, I don't only listen to orchestral music, my listening tastes are as broad as wide, but that's the clincher for me, and still these headphones lend a certain grain and congestion to the sound when the going gets tough, which disappoints me. When the music is clear, with only a handful of discrete lines to follow, they are amazing, but they are unable to give me the dynamics, bloom and texture of a 125 piece symphony orchestra playing Also Sprach Zarathustra, without sounding coloured and even compressed.