Your Krell has digital inputs so you can use a streamer to send a digital signal to it and let the internal DACs do the rest. Conversely, you can also let the streamer send an analog input to your Krell.
I haven't heard the Wiim but I know it gets lots of love here. I've had a Lumin streamer (no analog outputs, digital only) for many years and have been very happy with it.
Pick a streamer, connect it to your Krell, get it on your local network, download the app that goes with your streamer and away you go. It's pretty simple.