welcome, julienchina. my favorite first post ever!
well,well. i posted something like this months ago. i almost got run out of here,lol. that was before anyone really knew the ps1k.
now this is what is intresting. as you said the dt880/600 is outstanding(and better than ps1k) at acoustic classical recordings. alas, i do not listen to that type of music much. call me tastless if you must. i listen to pop/rock/electronic and some easy listening ala michael buble etc. there, the 250 ohm "pro" screams ahead of even the 600 ohm dt880. i will go so far as to say the "pro" brings pop/rock to life in way that even the likes of r10,010,he90,o2 cannot! ok, let me get my flame suit on again!
the 600 ohm may not be as revealing and airy as the ps1k on classical music. however the ps1k overall, as the op said is not so great at classical anyhow. the "pro" beyer however resolves/images pop like nothing else i have ever heard. i mentioned several times in several posts that i literally get scared as i hear things 8 feet away from my head when i am half asleep! the air is like delicate angels! these are as close to super high end loudspeakers as headphones may ever get, beyer did it before anyone else! yet, they fly way under the radar.
i will also mention again that stretching the cups so they close about 1/2" apart makes them sound much better and makes them more comfortable to boot. the pro's grip real hard. the coiled cable was actually a blessing beleive it or not,ymmv. i did of course replace the cable but i feel that has no bearing on how mine sound.
another thing i mentioned is the pro's like a hefty clean ss amp. like at least 3 watts. i am using a fully modded gcha which is 5wpc rms. don't be baffled by their low power limits. this holds true as well for the 600 ohm's. you need huge headroom with the 250's. this is bliss.
the funny thing is, i once thought the gs1k was all there was. then came the dt880 pro. now the ps1k does not impress. as already mentioned they are like a slightly more refined gs1k. for a lot more money than their already overinflated little brother. then there is the qc issue. i don't see my beyers ever suffering from such problems. don't even let me tell you where they are now(ny). like a lot of other peoples. overall i'd say the ps1k are a joke regardless of what you compare them to. now....go compare that dt880 to the hd800. i will reserve my opinion untill someone else speaks. i think you already know what i am going to say though
again, i listen to pop/rock/electronic.
music_man