I have a pair of Sennheiser mx 500, it's just that I misplaced them last year, and I still haven't been able to find them to this day (I know they are inside my apartment somewhere).
For non earbud listening/casual inhouse listening, I use a pair of Sennheiser PX100.
For critical listening, I use a pair of Sony MDR-SA500 hooked up to my stereo preamp.
For mobile listening, I interchangeably use a pair of cheap Sony earbuds and Etymotics ER-4S.
I lik the Etymotics ER-4S. They offer very good noise isolation. They are the only IEMs that I've found that I can tolerate to listen to on an airplane. Even with the ER-4S, I can still hear the engine rumble, but the noise is substantially less.
ER-4S also has a very lively sound, very fast transient response. But a bit lean on the bass.
The Sony MDR-SA500 is like a pair of ER-4S on steroids plus some serious bass drums.