Lots of Etymotic recommendations, and rightly so! I have owned and listened to a fair few IEMs and the ones that strike me as most competent for classical music are single-driver IEMs. The dual and triple drivers are good, but just don't have the same clarity in the lower registers where complex bass and lower midrange textures can really turn into a huge pile of mess. I'm talking about universal-fit IEMs only; custom IEMs are another kettle of fish altogether. I would take a pair of ER4P/S over a Triple.fi10Pro or SE530 for classical.
The HD555 is OK, but I find their sound very veiled, polite and lacking in energy. They are nevertheless fairly enjoyable to listen to.