here is my 2 cents

actually using an old core 2 duo pc as NAS is much better than spending money buying synology.

you can get a lot of function from that pc such as attach a usb printer to it and share it. it also can act as a torrent download machine. you can use it for downloading files from extabit, filefactory, etc

if you have guest coming over to your house and they want to check email or surf the internet, you can let them use that pc too.

you can configure that pc to become a home server. do whatever you want with it.