You should have suggested these to us new Philips fans James. I have been listening to the SHE9700. .Astounding. These are unreal great sounding. I can't find anything that is off on these at all in fact on careful listening of the 2 detail on the SHE9700 wins. That being said the detail on the SHE3570 is very satisfactory as well. Looking at the 2 earphones the SHE3580 and the SHE9700.
It wouldn't surprise me if both of these are using the same drivers. The housing diameter is exactly the same with almost the same sound. I think the SHE9700 has a better housing design for acoustics. The overall sound on the SHE9700 is a bit cleaner sounding. The housing has double the room of the SHe3580 the SHE9700 has more detail and a bit more defined on both ends. Otherwise the sound is almost exactly the same.
Let' not forget the SHE9700 are open back, which makes a big difference in sound. I actually was a big fan of the grand sounding SHE9800 back then and a bit of a basshead. Don't know if these are still available though.
Burning my Philips in but yet to listen to it today after. I did have treble harshness issues with the 3580 early on. Isurus at times did have sibilance but the Philips was pretty strident and fatiguing for me even though no real sibilance. Quite bright and harsh unless listening at low volumes. Should be settling down though. Didn't investigate exactly why since it would probably go away. Odd though; silver cabled TF10, EX600 foam out of the nozzle, Carvin EM902(even more treble than foam-less EX600), Isurus yet the 3580 treble bothered me after 5 minutes or so.
Try third party tips, the 3580 stock tips lack quality and are prone to sibilance.