Before we dive deep into this topic, we need to clear something up for some people reading this, What even is a Network Player/Streamer?
A Network Player is basically a Digital Audio Player(DAPs) for desktop/home use. What? It’s basically a computer with a processor, memory and storage, sometimes even a display. It allows you to play music off in-built or attached storage or even wirelessly from a media server or a NAS(Network Attached Storage). You can either build your own or buy a finished unit running modified or custom software. The advantage of such a device is that they are dedicated for audio and provide a myriad of outputs, some that aren’t even available with regular computers. Some of them even work as CD Player/Transport or also function as DAC, making it a complete player. Another advantage of such a device is that since it is dedicated to one purpose, it doesn’t need the heavy duty hardware that PC’s do and thus don’t even need the kind of Cooling Fans, which generate a lot of noise and vibrations, which is not ideal for outputting high quality audio.
As a matter of fact, if you’re not really looking for the “Best Of The Best” Audiophile solutions, you can get a bunch of standalone devices or integrated systems, for not a lot of money. Chromecast Audio, Sonos, etc, are great examples of such standalone devices, you do also get speaker systems with these services integrated, like Google Cast, Airplay Devices, etc.
As far as what I think of the Higher End Players, if you would have asked me a couple years ago if I would ever buy such a thing, I would have laughed at you and probably said, “Don’t be ridiculous!”. However, over the last few months, I have looked at a couple such players and said to myself, “Wow! That’s so cool, I’d love to own it.” Well, what changed? Simple, it's a hassle to build a new PC for every node, you don’t want to invest in expensive fanless chassis, or USB Purifiers or USB Converters for the best sound(USB is crap for audio and that’s a whole other topic), all that stuff gets really expensive really fast. You don’t even need to spend a few thousand dollars for such a streamer, you can even build something really simple with a Raspberry Pi 3 and add S/PDIF or other audio output modules, as you please and run custom skins of Linux. Sure you’ll have to muck about with software (Or get systems with pre-installed software and modules) but if you are technically inclined, it’s not a lot of effort really and you can build a really nice, high quality node for cheaper than a mid-tier smartphone. Or you can always go for something like an Auralic Aries, Cayin iDAP6, ELAC Discovery or any of the other countless options from Sony, Marantz, Denon, NAD etc.
This is not saying you'd be stupid to re-purpose an old Computer or build a new system, they are so much more convenient. Even though they will never deliver the quality that would satisfy a purist, without adding a bunch of hardware for reclocking and USB Conversion, they can do so much more than just audio. You could just add a beefy graphics card and have a better gaming experience than any console available on the market, you can browse the internet and serve up all kinds of media, with or without the need of a NAS. However, for the uncompromising Audiophile, such Players/Streamers are an excellent option to look to for use as a Transport, whether it be a $50 Raspberry Pi setup or a Multi Thousand Dollar Component by DCS, Chord Electronics and the likes.