Angelopsaro, I wouldn't say that SHP5401 has similar sound signature to D1001K, the whole reason why D1001K/CAL have such highly praised sound is because of Fostex bio cellulose driver used. The king of dynamic headphones Sony MDR-R10 (worth some 3-4K) also has bio cellulose driver. My understanding is that it was originally developed by Sony before Foster. The sound is very delicate, soft and no fatiguing at all, its bright but not too bright, it has just right amount of highs. You really need to listen to them to understand. They do sound much better than Philips. Philips without doubt also has some kind of paper drivers, this is why the bass is so good(actually paper does produce the best bass) and this is why they are so fast. But the driver they have also has the typical paper driver disadvantages which is some lack of realism in the sound if you know what I mean.
I have no issues with isolation, nobody in my office complains. If you want to walk on the street with them, then yes the isolation becomes a bit of an issue and you find yourself slightly increasing the volume. When I go outside I use my HF5 anyway because its a winter now and IEM is much more comfortable if you want to wear a hat.