Raspberry Pi DAC - what do I need?


Hi, total newbie here - as will no doubt become clear from my questions.

I have a Google Chromecast Audio that I want to connect to my NAD C326BEE integrated amp via an external DAC, in the hope of improving the sound quality over that provided by the CCA’s built-in DAC. The amp does not have digital inputs.

I would like to build this new DAC using a Raspberry Pi and whatever Pimorini components I would require - I need guidance on what these components are.

My desired chain is: CCA->(TOSLINK)->DAC->(RCA)->NAD Amp

So I assume the DAC will need a TOSLINK input and RCA outputs - is this correct or have I misunderstood?

Having done some investigation, I am considering buying the following:
Raspberry Pi 3 Model B
Pibow Audio case
Pi-DAC+ or Pi-Digi+ or…something else?

As you’ll see, I’m not sure which Pimoroni item(s) I need to provide the basic DAC functionality. If anyone is able to advise on this - and anything else I might not have considered - I would be grateful.