best audiophile IEM...ue10 custom, ue11 custom, among other high cost customs.
best top line selection IEM ( no particular order )...shure se530, ue triple fi 10, klipsch image and custom 2/3, etymotic er4p, westone um2 soon to be succeeded by the ''3'', sony ex700.
best mid line high def selection...shure se310, denon c751, ue super fi 5, sennheiser cx95, jay's Q-jays, etymotic er6i
best low def ( generally speaking, not as highly regarded ) selection...sennheiser cx500, denon c551, shure se110/210.
just a nice selection on in ear options in their respective classes. the selection in the top line class is a case of not whats best but simply what sound you prefer. such as...warm,cold,analytical,fun etc etc. there is no best IEM.