Any alternatives to Astell & Kern DAP's?

I'm looking at the A&K AK 100 -2 but at $900 (cheapest I could find on the internet) it caused me to pause. Is there any alternative that would be less expensive? The Ibasso DX90 is something I would consider but the reviews I've read are mixed. Would appreciate any feedback you could give me. thanks.
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.
Used 160gb ipod classic was my solution.
The iBasso and Fiio units have gotten good reviews. There are several models of each starting at $99...

I prefer the sound quality of the latest iPod Touch 64gb model. Plus it can do Pandora, Spotify and Tidal. For travel I like a device that can fit in my shirt pocket. Have heard good things about the Sony NWZ A17.
Present: 7 Gen iPod 160 gb + Fiio Andes (E07K) + Kef M500. Plenty of detail, space and very good bass.

Future: Lenovo Vibe Shot + Oppo HA-2 + Kef M500.
The AK can certainly fit in your shirt pocket.
Indeed, it would fit very nicely...
I'm leaning towards a fiio x5 which supposedly supports24 bit /192. It can be had for about $300 new or $250 used.....stay tuned.
PONO. Just ordered one with the balanced cable for my enn 650. cant wait. planes will be fun again.
Fiio X5 and the Hifiman units are worth contenders. headfi has tons of reviews and detailed threads on them and related topics.