May I just say that this thing is just amazing. Now, I'm pretty easy to please.
I'm always about the enjoyment of music but we all know what headphiles can do to you, even minutely.
I don't usually nitpick as much as others still, the usage of the istreamer, or any same device I reckon, will yield an improvement that a person like me could appreciate.
I've never tested the Pure i20, which I got first, thru any HP/IEM of mine since I bought it for transport purposes for my humble speaker system. But, man, testing the iStreamer now - the music, if I may, is soaking in brand new light. It gives a 3D feel for my ears. The songs I tested/listened to were the freshly ripped Makita Kang Muli by Sugarfree, and Sideline Story by Jay-Z-apprentice J.Cole (no hip-pop here). ;p
Makita Kang Muli: The background voice is more... emotional. The notes on the strings sound more separated and had distinct rise&fall - cadence? It's like pinlights highlighted each component of the song by how separation was presented.
On the J.Cole track, the bass line had more groove to it but not by much; overall detail is better. But the thing I noticed the most would be the double take on the chorus/hook. It is fairly obvious how it was intended to be heard via straight dap config but the separation would tell you really what is up with that double take.
I used my dt1350 but I would guess better HP's and Amp would paint the iStreamer's capability better or if it's worth it or not so YMMV.
OT: I don't know why some would say the dt1350 has no bass. I tested it with the rig stated below and it's there and even more prominent. It reaches low - very low - to my ears. Even with a naked rig straight up ipod style.
YMMV again
Ipod Touch 4g, songs @ 320kbps > iStreamer > FiiO E9 > dt1350
