Interesting. My PF IX have just experienced a rebirth since getting the 1601SC. I am now willing to take a lot more risks with them so I have started using them directly out of my Rockboxed Classic, not only walking around my flat but downstairs in the garden area (which is fairly quiet) while smoking a cigar...
Where isolation is not essential, listening to Jazz in that bell tower sound stage while out and around - or just moving around - is exciting. These are incredible (non-isolating) portables.
It helps that I get a really secure fit. (I couldn't do this with the 1601s. Anyway the 1601SC is not leaving the security of my desk computer audio area.)
I am off to Beijing and then far northern China on Sunday and for the first time I will be taking the PF IX with me. Very cool.
The case is so secure, I keep mine in my bag with me at nearly all times. Great to be able to pull them out for a quick listen when given the chance.