Any alternatives to Astell & Kern DAP's?

Check out the Pono review in new Stereophile

I'm still trying to figure out why one would buy an Astell & Kern or a Pono? Other than the Astel & KErn do appear to be quality devices albeit specialized ones that are also somewhat pricey, but not so much on the high end audio scale of things.

For example I run PLEX mobile apps that cost $5 per platform (Apple, Android) which support all high res audio and video formats for streaming and this works very well. How good it will sound will depend mostly on the device used, largely DAC quality, and what headphones one uses to listen. Some headphones and of course any decent speakers will also require some kind of outboard amplification, but there are many common commodity phones, tablets, portable amps, headphones and speakers to choose from.

Maybe someone can help me out?

So I guess I am saying running $5 Plex mobile app on a good quality tablet or mobile phone is an option.

I also run Plex at home on amazonFire tv box with toslink out to DAC in my a/v second system (see my system pics) and this sounds pretty much as good as the Logitech Squeezebox to same dac and system. The two are interchangeable in terms of sound quality for teh most part I would say though features for users, GUIs, are not the same but share a lot of teh core functionality that most people would need in order to stream higher res music/audio plus video to boot.

HIFIMAN 901 best SQ but not the best interface.

What the AK devices bring to the table is a portable, high quality inboard DAC.