So, I received the 7520 and Z1000 today and I should receive the Focal Spirit Classic tomorrow :)
Initial impression on the 7520 and Z1000 are 1: My ears completely fit inside both!!!! :D And the 7520 is even a bit more spacious than the Z1000, but the Z1000 isolates slightly better. The Z1000 also has a bit more clamping pressure than the 7520. Otherwise they look similar, except that the 7520 is all black.
In terms of sound I can't say much yet, need to give them a closer listen, but they do sound slightly different. I guess my initial impression is that the 7520 sounds a bit more spacious and has slightly more bass, or at least the tuning is different where the Z1000's bass sounds a bit more rolled of compared to the 7520 (it's a slight difference though, but my test track for that is the first track on the Dark Knight OST, around 3:20 into the track where a deep sub-bass enters the track).
Anyway, will let them burn in overnight (just in case) and will also compare with the FSC over the weekend. But I suspect the FSC won't be nearly as comfortable as these Sony headphones.