Good DAP, DAC, or amp for xb90ex, EPH100, DN-1000, and ATH-M50x?

[thishereschlub]

I've been getting into the headphone game for a couple years, and now I'm looking at my first hardware purchase.
 
I currently own: EPH100, DN-1000, MHA750, ATH-M50x, and am awaiting shipment on XB90EX. Next headphone purchases (later this year) will be V Moda M100s and a high end custom IEM. I currently use a Galaxy S5, mostly with Spotify at Extreme Quality, and some FLAC files on the S5 or a 5th Gen iPod.
 
I'm looking for either a DAP with streaming capability, or a DAC and/or amp to pair with the S5. Must be portable, and my budget is about $300.
 
I want to get the most I can out of my earphones, but I don't want to make an unnecessary purchase. I would like a recommendation suited to the headphones I own/plan to own. I have read through guides and FAQs but am still lost and not sure where to start or what gear I should even be buying. Will I get more improvement out of an amp, or from a better source, or some combination of both?
 
Huge thanks in advance.

 

[kimvictor]

I don't see much reason in just getting an amp or a lower end DAP.
 
Here is the RMAA measurement of the S5 LTE-A version(which does use different AP from the S5, so it's not a guarantee that the regular S5 will sound the same, but it likely should). It measures fairly well at 108dB SNR. Most lower end DAPs would have a similar level of SNR, but probably more power. None of the iems/hp you've listed really requires much power, so you won't find much improvement if you end up buying a lower end DAP.
 
If you absolutely must have streaming capability, your options are likely limited to Android based DAPs, and most decent Android DAPs cost more than $300.
 
So I would say you should invest in a small DAC/amp you can pair with the S5.