what i mean is a device that looks like audio equipment and can be connected to your existing stereo system that is essentially a sound card with a large hard drive, so you can store music files locally. it would be a specialized mini pc with a high quality dac and large storage capacity, plus a few usb and other ins and outs, for external storage.
you can buy receivers or bluray players with usb connections that let you scroll through them and i could accept that and have considered it for a secondary system (in my bedroom). but i can't imagine scrolling through a 5 tb drive looking for something. i need a search and i need a file explorer. i need an os.
you could in theory do this in one piece. a little mini pc running a specially distributed linux distro with a good dac and a large fanless drive capacity and a kvm out and maybe a remote touchscreen would be something i'd buy. you'd just send the audio out into your amp, or maybe it even has it's own amp, with inputs to connect a cd to it instead, and direct speaker outs.
the streaming devices strike me as useless.