Your Marantz is probably all you need in DAC. Now you you just have to feed it some digits—i.e., get a digital source. Since the main reason that you are doing this is the (probably fruitless) desire to look cool to younger generations, I would keep it simple and get a Bluesound Node2i. It will connect to your Marantz in multiple potential ways. You can connect to the internet through either Wi Fi or Wired. You can get every streaming service imaginable, such as Spotify or Tidal. And it has Bluetooth, so your kids can stream their music from their phones when they visit. Bluetooth is a step down quality wise, but the millennials won’t know or care, and it can still sound pretty good.
Happy Holidays.
Happy Holidays.