DH Labs makes two very good optical cables - I have used the one in this link many times and a friend just put one from his MAC Mini to his Schiit DAC and it sounds pretty amazing
https://silversonic.com/products/digital-cables/toslink-optical/They also have a glass one which is probably better better
https://silversonic.com/products/digital-cables/glass-master-toslink/To get anywhere near that level of performance with a good SPDIF RCA cable would cost more than either of these two
The DH Labs SPDIF RCA cable is not as good as their optical cables
I’ve had other optical and SPDIF RCA and TOSLINK cables from companies like Chord, Van den Hul and prefer the DH Labs offerings by far
KLE Innovations also has a couple of exceptional SPDIF RCA cables for around $200 and $300
I happen to have the Node 2i and it’s analogue section is outstanding i.e. IF you treat it to great cables.
But it might be a more cost conscious solution to use the onboard DAC in the Receiver - the analogue cables can get quite expensive
Regards - Steve