For optimum sound quality, we recommend to take advantage of the internal DACs of the CXN. This means that the CXC would be connected to the CXN via S/PDIF, and then the CXN connected to the CXA-80 via balanced XLR cables, or unbalanced RCA cables for the CXA-60. This does mean that you would have to select the digital input on the CXN before sound comes through to the CXA.
However, for a quicker and more convenient connection, you can connect the CXC directly to the CXA via TOSLINK optical cable.
For the best of both worlds, you can combine both of these connections for different listening occasions. The S/PDIF and TOSLINK optical outputs work simultaneously on the CXC, so you could use the direct connection to the CXA for quick convenient listening, and use the S/PDIF connection to the CXN for optimum performance and quality.