Digital music through my Hifi

[Dead Eye]

A NAS is complete overkill for just music, you want something small and simple to use. Also you are correct, a NAS is usually a dumb system that just provides file storage and most standalone systems do not support any sort of built in control or audio output. A simple PC would be better, but realistically that's still going to cost a lot of money.

This brings us on to an android tablet is just a hard drive with a decent colour display; and there are plenty of apps to choose from for organising and playing music. It is effectively a handheld mini PC and can cost a fraction of the price. The fact that it is mobile will make transferring media to and from it fairly simplistic without any complicated networking - I personally use WiFi and an FTP setup to transfer data, but that's going a bit far beyond the simplistic approach if you aren't overly tech savvy

Some modern amps can be controlled remotely from a PC / Mac / Phone via your local network. The amp connects to the network and allows other devices to stream media; my mum has this setup with an iPad