I've used etymotic er4s with the e12 and they work really well together. There's enough power to produce tight and punchy sound, although the soundstage is very limited, which too m is not an issue. I do like the sound being upfront and intimate but may be that's just me?

Excellent review. I've tried some AK R01 and would stick to the etymotics, may be because I like to the all round brighter sound and tighter bass of the etymotics. I was amazed by a pair of HifiMan 500s I just tried by how spacial the music sounded but the sound just didn't have the tightness...