As a sidenote, I am surprised ER4's would EVER be recommended for classical.
IMHO classical needs a vast, large full sound to capture the symphonic experience. ER4 does not do this. Also, with so much going on and so many instruments you need an IEM that can handle "busy" passages of music when it gets going. This is another fault of ER4. But I would definitely agree on the UM3X choice!
I've heard amazing things about the UM3X but it's much higher than $200 around here in the United States. And I won't be using an amp.