I would first research what is the best digital input on the Pontus II. Some DAC's perform better with I2S, others with USB. This will determine the ideal device feeding the DAC. The last link in the chain before the DAC is the most vital; components further upstream can be isolated by streaming over a network–lessening their significance.
Owning a Roon Nucleus I assume you are using Roon? If the Nucleus is running Roon Core, it is not only playing the role of streamer but also the role of server. In this case I would suggest offloading the streamer/Roon endpoint duties to something like a Sonore ultraRendu or microRendu. Connect either of these devices to your router/switch/modem over ethernet, and as long as they are on the same network as the Nucleus you can use them as Roon endpoints. Then go USB into the DAC.
You can supplant ethernet with fiber optic for even better isolation, but cost and complexity increases.