I have the brainwavz m2 and vsonic gr02 bass edition which both work great on the n900 and have great build and sound quality. The m2 is a little prefered because I really like the bass and I find the rest of the frequencies to my liking (the gr02 BE over-stressing the higher tones a little in my opinion).
I don't know about over the ear headphones because I prefer them to be in ear.
Check out this link, it's a useful review and comparisson of over 250 iem's:http://www.head-fi.org/t/478568/mult...added-09-05-12