Just got mine. From a non-audiophile point of view, it's a decent pair of headphones for listening to bass and pop. I don't know if it will perform better with an amp but it's alright with me out of the box, plugged straight into my Samsung Galaxy S4.
Vocals are clear, bass pops out just nice for me. Nothing amazing or shocking coming from a xiaomi pistons v2.0, but they're decent. I've got slightly bigger ears and the earcups cover them just nice.
Design-wise, I was surprised that they actually look smaller than the pictures I've seen of them. It's mainly plastic but isn't low grade by any means. The adjustable headband is quite precise in getting the fit you want.
So far I'm not gonna do any mods to it. Will keep it simple and not be an audiophile about the whole thing. He he.
Nice buy, it'd be quite dark sounding coming from the pistons. Changing to HM5 pads helped with comfort and slightly with SQ. I modded mine with Dynamat extreme in the cups but it only made them even darker lol.