used to rip CDs...
...which will only be used to rip CDs and play FLAC through J.River.
You can build such computer with a mini ITX motherboard and fanless components. If you use a pico PSU, a fanless chassis and motherboard, a SSD and no hard drive you will have absolutely zero noise (apart from the eventual optical drive).I recommand Streacom chassis, as they have very good passive cooling abilities, and can handle the heat of most Core i3/i5 CPUs without problems. I own a FC8 evo, and am very happy with it.
So the HD with music would be external through USB? Is that ideal?