Excellent headphone amp for nomadic entry

I was looking for a quality audio solution to pass the time in transport. Having (too fast) acquired an iPod Nano because of its relative space / capacity very interesting, I quickly realized its limitations, despite the encoding quality of my music.
After some research on the Net, I found the Fiio brand. I started with the E6, given its low cost, successor to the highly regarded E5 and even lighter than the latter.
I am completely satisfied. Its footprint is minimal autonomy more than correct (ten hours) and the Nano is transfigured.
The sound is higher but also more detailed, precise and warm at once.