last count i had 26 pairs of Sennheiser's, so what d'you want to know?
The CX range goes down well, with the counterfeit market as well as enthusiasts so be careful. The same goes for the PX100/200.
http://fakeheadphones.com/
I've currently got my HD25-1 headphones on listening to 'Africa - Toto. The HD25-1's are my all time favourite headphones. Small ... ish enough to be potable, easy to drive, every part is replaceable, cable, ear pads, drivers, headband everything is replaceable. In fact you could buy one part at t time and build you HD-25-1's that way. The sound is much brighter, less veiled than 90% of the Sennheiser range.
The new HD range is quite good HD218, 228, 238. portable very crisp, but my HD238's don't do rap or beat driven music without a protest from the diaphragms.
Sennheiser IEm's I don't really like although I have the CX300, 400 & 500. I prefer Ultimate Ears IEM's, although since being taken over by Logitech UE's customer service has gone down the pan.
I'd buy the PX100 over the slightly more expensive PX200, although i don't like PX100 styling. But i prefer the iGrado's over the PXs'
Generally, I prefer Grado over Sennheiser (bar the HD25-1), and Grado are bringing out an IEm version, the GR8 $199 and IGI $89, don't know whether they've actually been released yet.
http://www.soundearphones.com/shop/317-grado-gr8-in-ear-earphones/
http://www.soundearphones.com/shop/318-grado-igi-in-ear-earphones/
What else do you want to know?