I know the SBT is now out of production, but they still seem fairly available - this may change, so you may want to buy sooner rather than later. From digging around, the only option I found that seems similar (quality & ease of use wise) is the Sonos Connect, though it has no screen, so you will need to use a smartphone app to control it (there is an official one) - or buy their expensive remote control.
A NAS is just a storage device - no ripping facility, so yes, you would use your PC.
I'm desparately trying to remember the name of the company that was offering well thought of prebuilt PCs with all the ripping software set up and ready to go - so it acted as the NAS/media server and ripping device... and I just have -
http://www.vortexbox.co.uk - this might be worth looking at instead of a standard NAS.