Pros: Excellent detailed sound, multiple inputs, USB charging, long battery life, handles 24/96 over toslink, selectable gain, socketed opamps
Cons: less brand recognition than some competitors
That's a link to my full review. In summary:
the Leckerton UHA-6S is one of the best portables amps I've used (and I've used a lot). It has a very high end sound, both as an amp and a DAC. The battery life is very good, it charges via a simple USB cable, it works with almost any headphone thanks to dual gain settings, and it even has socketed opamps inside for people who are inclined to tweak. It is built by a small audio company in the USA who offers excellent support, a 30 day money back guarantee, and a full 2 year warranty. There's really not much more one could ask for in a portable amp. You can save $20 by getting a USB only version if you don't think you will ever use the toslink input, but I think it is a nice option to have. I don't understand why this amp isn't more popular.