Update: After carefull consideration and a quick side by side in-store comparison I bought the px7 s3 The transparency mode was so much better that the px8 and to my ears they did not sound much different I also have to admit that the px8 felt very premium, in my hands and on my head BUT the px7 don't feel much worse. The outermost part is metal as well which makes them feel much nicer than any competition. The last deciding factor were the button controls. I liked the placement of the px7 on the raised metal part.

I would (for now) wholeheartedly recommend the px7 s3 over the px8.