Back off topic... as many of the above posts highlight including Twerk's, this thing is a journey. I think jumping straight from something like Pro-900 to TH-900 may be too fast to appreciate the differences, but each to their own. It took me quite a few purchases and headphones to work out what signature I was after.
I went (approximately) over the last 5 or so years: Shure srh840 -> Beyer T70 -> Pro-900 -> HE-400 -> TH-600. Each and every one seemed like a fairly significant upgrade to me and I was hearing and appreciating new things in my music collection. If you go straight to the 'summit' you're going to miss some of that journey and also you'll still feel the need to 'upgrade' one day - to what, $5k 'phones? There's nothing wrong with lusting after an 'upgrade' but being a realist and putting a hold on it until you can afford it. Its good sometimes to appreciate what you have until you're ready.
To me the TH600 was a massive step up from the HE-400 in so many ways, and easily worth over 2x the cost. But at the same time I remember being blown away when I first heard the he400s and that planar sound. As I also was when I got my first good pair of studio monitor speakers, until I eventually realised they were far from flat and were being heavily coloured by the acoustics of my room (reflections) - which is why I love headphones so much, the only 'extra' colouration may come from the source.
Anyway, personally knowing that the TH900 are only 5-10% better (or different) than the TH600, they're not different enough for me to upgrade from 600 to 900 (ever). Not interested, period. If I were to go a different route one day it would be to wait for Fostex to bring out something new and even better, or jump to something like LCD-X or Stax SR009. But to me those are not headphones for listening while looking at a computer screen and doing other stuff. They are for closing your eyes and sitting there and doing nothing but listen. Something I don't do very often, and I doubt many of us here do much. So its a bit of a waste IMO.
Anyways, a great home set of 'phones and an enjoyable office set will do me fine.
It is in this hobby that 5% - 10% increase in quality that costs the extra $. It may be worth it to some to others not. If I could do it all over again I would try and shoot for a top tier headphone right off the bat, and in turn save some money. I was also a believer that the differences were so minute between a flagship and its siblings that the cost associated with such upgrades were not worth it.
I have learnt otherwise over the years. And although I agree the journey can be enjoyable, the idea of owning a top tier headphone really rocks also. Given a few more years here or in the hobby in general even your opinions may change
Besides, judging by what headphones TWerk has owned (owns) I'm sure he feels he's "journeyed" enough.
Once you begin living with the "higher end" your point of reference changes considerably and so does your ear.
Edited by Mortalcoil - 5/4/14 at 10:23pm