If you are only want to have a central place for streaming media, a router with HDD will get the job done.
It’s seen as a solution, and that’s how you should choose it. NAS is no more seen from a hardware perspective. You can not only add your personal files to a central server, but it can also backup your PC over time, and help you restore in case of failures. The next big advantage of having a NAS at home is Backup. in one place and let everybody access it. You can centralize all your common data like Songs, Photos, Videos, etc. It’s like a hard disk which is available over your WiFi network for everybody.
This situation demands NAS or Network Attached Storage.