ok so I received the t50rp mk 3, in the meantime I picked up some used LCD3f. Being the only two headphones I had home I did a quick fun comparaison.
The T50rp mk3 sound AMAZING: if the lcd3f are 2000$ the fostex should be at least 800$ !! they're very balanced. good bass, not very refined and a bit slow but they have a great impact. the highs are mellow they don't tickle but they're defined enough to enjoy. The mids are very good: the female voices is a little bit distant but very smooth and clear. They remind me of my HD650's. I have to stress how balanced they are ! very musical and jovial headphones. As for the comfort I find them very comfortable, the pad sits nicely on the ear, it's pushing the ear inwards a bit but I don't see why people rush to change them ?
The LCD3 of course have more detail, more layers, everything is more defined and refined, soundstage is wider, highs are clean and clear. But I have to say, overall they sound less playful than the fostex.
I would describe as the new T50rp mk 3 as French, they know how to enjoy life, they do quality work but don't seek perfection, they like to have fun but sometimes a bit moody. The LCD3 are German, they're very strict, they seek perfection in everything, they won't quit until the job is done perfectly in all it's small details. but after the work is done they're not as fun or as charming
Anyway for 140$ that I paid they're an absolute steal. it's really hard to justify the 2K price of the LCD3's after listening to these