W4R is working on iPhone/iPod, as well as UM3X, I tried both of them. No one of these IEMs needs an amp, but all of them work even better with an amp it's everytime like that
UM3X is better on voices, much warmer than the W4R, which are more polyvalent and transparent. If you like EDM and indie rock, which are very different music style, I would recommand you W4R and perhaps SM64 because of his warm vocals and smooth bass rythmic. What is exactly your spending limit ?
if they need an amp to sound better, doesnt that mean that they need an amp?