Their is so much crud talked about digital files its getting annoying to me.
Your NAS is simply a small server, it doesnt process a file for any type of data whatsoever when its sending it to a device, it simply sends the data and the device on the other end processes it - THAT device can matter when it comes to final replay of music/video etc. The NAS just sends data.
The things to look for in a NAS are :
Wired Connection - you should go for Gigabit interface, any switches (please dont use hubs) in the path of the data must also be gigabit devices for the benefit to take effect, however 100Mbit is fine, even for quality video streams unless there is perhaps 12 people in your house constantly streaming off the device.
Wireless - negate the cables, at the potential cost of less reliability in especially 'noisy' RF situations. More bandwidth the better, most devices can manage a reported 108Mb connection nowadays - yes its scientific best scenario but a good measure.
Storage - More is better, always. Take into account using FLAC you will need about 15Mb per 'normal' song. If you go original CD Quality WAV format - make that 10Mb per minute of tune.
Processor on the NAS - get a modern, good make one, and its unlikely you'll go wrong as i believe nearly all now are using multicore processors that do not get in the way of the data delivery (ie slow it down). Again there is no real processing of the file, but there is in so far as organising and sending it goes - old NAS would suffer speed drop due to this.
The cables - do you really think that if 'standard' Cat5 cables introduced so much trouble theyd be in use now in most computing environments ? the answer is NO btw. Us nerd types value our data transfers more than the audiophiles value the frequency response.
Ive never laughed so hard as when i saw an 'Audiophile' Cat5 cable for sale at £95.
🙂