I am coming from a Fiio e11 which is a powerful little amp and this is an amazing upgrade. For this review my set up is a 6th Gen Nano with an L9 to the e12 switching between a pair of UE Superfi 5eb and ultrasone580s (I cant wait for my XB1000s to come in to really see how well these two can play together). The best way to describe the sound is that someone took the mids and highs and threw them all the way to the other side of the room while leaving the bass intact. The clarity and separation is greatly upgraded from the e11 I would rightfully say this amp is twice as good once you get accustomed to the sound signature  which says a lot. This definitely warrants the the price difference. The only issue I have is with the volume. First the knob is a little tighter and tougher to move than the e11. Second is the gain. I had it set to 0 and had it on full blast and though "well this isnt too special" then switched it to the other setting, 16, which I'm beginning to think is the Chinese symbol for "dear god why would anything ever have to be this loud." Another thing to consider is that this thing is pretty big. Its definitely portable for a guy wearing jeans but I dont know about for a girl's pants or use at the gym. Its about the size of two ipod touches on top of each other.