How do you find its isolation and leakage? I can imagine Sig Pro must be better in this area. I bought one pair of hd600 but just found that I couldn't use it in office because of sound leakage. So isolation/leakage is a quite important factor. I don't consider th900 seriously just due to their poor isolation/leakage performance(from what I have read so for).
Portability is another thing to consider. It's not critical but will be a big plus. I spend 2 hours on public transport everyday, and currently and currently I am happy with my fx850. My understanding is that Sig Pro is easily portable but Blackwood is almost not.
To me, sound is definitely the most important thing, then isolation/leakage/portability. I don't mind adding an amp. I will probably buy one even for Sig Pro.
So what would be your option taking sound/isolation/leakage/portability into account? I know this is a subjective thing, but I'd like to hear your opinion:)
Sig Pros would fit the bill here, and they have the benefit of being very easy to drive. If you're okay with something a little bigger, I'd highly recommend the ZMF Blackwood. The former is a bit more detailed and has extremely extended but flat highs, and the latter has a more natural, richer tonality. I do have to say if you're okay with the size and having a small amp, the Blackwood is really an excellent option. I did end up deciding on the Sig Pros between the two, but the decision might have been different if I didn't already own them.
I haven't heard the AP yet, but from what I understand the treble is a bit more forward.