Since I'm still pondering wether to keep the Px8 I dug out my APM today, which I rarely use -- another reason why I'm still considering if the Px8 is allowed to stay: I already have a not quite cheap wireless over-ear headphone lying around mostly unused...
And interestingly I have to admit that the APM caters more to my personal preferences soundwise than the Px8. The APM offers a bit more treble (though I still think there's a slight tendency to hardness in the upper mids) and digs down deeper more freely. Mids on the Px8 are nice, bit I'm missing treble a bit, at least in direct comparison which doesn't say much about everyday use since it tends to exaggerate minor differences. The APM also feels more spacious to me, where the Px8 is more intimate. This is with both connected to an iPhone using AAC obviously, my main use case.
Switching back to the M-100 still gives me the most fun presentation... yes, its wired. No, I don't mind much if at all. One thing less to keep charged...
Things I really like about the Px8:
* Looks. The 007 color is keeping a very nice balance between not black and too splashy, the red accent is nice.
* Build quality. It feels good in hand (despite the fact that the cups don't swivel to the same extent somehow
* Comfort. Feels nice on the head, cups are deep enough, the leather is soft and supple, the memory foam well balanced.
Regarding ANC it's not a contest, the APM wins hands down. I don't have a strong need for that though, the passive isolation of e.g. The M-100 is sufficient for me even on the underground. Head detection works flawlessly with the APM, while I did not even test it on the Px8 after reading others experiences. I don't need that either.
Overall I think the Px8 is going back, sad as that makes me. I think it would spend most of its time unused until I would decide to sell it at a loss... which is a waste in every dimension... its a nice headphone that should go to someone who actually uses it.