I think I might try the rPi option.
One can connect a touch screen to it when not networked, or control it with a smartphone when networked - could even use your phone's wifi hotspot as your network and control the pi with a tablet or ipod touch or something. On-board storage from SD cards or a USB hard drive, with the ability to access NAS if you need.
Also, you can get add-on audio modules from https://www.hifiberry.com/- dacses, spdif-outs, ampses, or just use your own USB DAC.
And it's cheap, so it's not a tragedy if it doesn't work as well as I want and I end up turning it into a Minecraft box for the kids.