I would research what will match well with your IEM's. What sound do they have and what sound do you hope for. Base your amp choice by the sound signature you are seeking. Something warmer, go for the TTVJ, cooler, the ALO RX MKII. If size and shape isn't as important look at the RSA amps. The have a heavier bass, but still very clean. And their balanced amps are great. But the shape can create a clumsy bundle to carry with you. That's why I like the slim amps. But if you are only trying to power IEM's then look at the Pico Slim or the headstage arrow. I haven't tried the last two. And I certainly haven't tried all of the RSA Amps. Or for $60 try the JD Labs altoid amps.