well, it's a difficult choice. First step is to be aware of which kind of music you listen the most, then decide HOW you want to hear that music ("as it is" or with some kind of boost in certain frequencies).
Earbuds can have a "flat" signal response or "colored", the preference is totally subjective and mostly depends on tastes and, eventually, tasks you have to accomplish by using such gear.
For example: I have Westone UM3X with detacheable cables, they have a totally flat signal, which is needed for my works (mostly equalization and post mastering) and I totally love UM3X even for listening music (they are perfects for Classical and Jazz, as no equalization is required -nor welcome-, and they have awesome soundstage with solid neat bass with just a light equalization for rock/metal/whatever else).
Using Comply foam it's possible to achieve -25db noise isolation, which is very important when doing certain works (or to listen in heavenly peace
), and you may need an headphone amp only if you buy a pair of earbuds with high impedance, otherwise you won't notice any benefit.