oqvist, that's a tough question to answer. It depend on how forgiving you are of electromechanical devices that were built to a price 30 years ago. That's most of the answer to your question right there.
Yes, the NA-market Fostex T50 was good stock, but it's too rare to recommend and there have been disturbing reports of lookalikes that don't sound the same. Besides, many here would call it too bright (it was meant to appeal to fans of electrostatic 'phones of the time, read Stax SR-X). It certainly pointed the way to the modern orthos now being sold by Head-Direct and Audeze, but it's tough to be forgiving of its flaws when you've paid big money for one that would buy one of the socalled Neo Orthos, which are, as you'd expect for 30 years of technical advances, much better and don't really need any modifications unless of course the purchase price has made you really picky. And it should.
Eventually, the companies that stay with this high-end ortho thing will realize how laughably easy it is to tweak the sound of these 'phones at the factory and they'll offer variants: HRTF (aka diffuse-field), mellow, bright, flat, tilty, and so on. Color code 'em (hot pink for bright, dark blue for depressed and sedated). Heck, they could offer mod kits and even pack them in the box the 'phones come in. Open a little door and slip in a dot, a star-shaped felt insert, an earpad vent, etc etc. Cost: nearly zero.
Some day.
Anyway, do any other orthos sound good stock, I hear you ask. Well, sort of.
scompton's already mentioned the Yamaha YH-1000-- same situation as the T50. For what it'll cost you to get one (~$900), it ain't that good, plus there's a reliability problem.
Many people, like scompton, have enjoyed using the Yamaha YHD-1/2/3 in stock form. They're very mellow and warm (too much for me, but that's me), and the bass is rather fat and loose (ditto), but the ortho goodness shines through. They're not that expensive, they're unique, they have unbeatable style, and you might like them.
Many people also like the current-model Fostex T50RP in stock form. It's not playing up to its potential, certainly, but it's cheap (by current standards) and available whenever you want to buy one. Easy to forgive something for underachieving when it's only ~$60 and built like a piece of pro audio gear, which it is. The problem comes if you ever want to draw the last drop of potential from its overachieving little driver. Do a search for <thunderpants> to get an idea of the effort involved-- that's why scompton warned you away from current production Fostex. The older Fostex ('86 to '06) are, just as scompton said, much easier to modify (and even more affordable when you can find them) but don't sound all that good in stock form. [shrugs] Whaddya gonna do.
Lastly but not leastly, there's the HP-2. Its smooth, laid-back (WAY back) stock sound can be lived with very easily as your ear-brain becomes educated and the need to get past the compromises of Yamaha's 1976 design decisions starts to bite. When that time comes, it's not the easiest ortho to work on, but it's simple and it responds well to simple mods.
That's probably far more than you wanted to know, but it should answer your question and throw some context over the topic.
