Using the digital output of the CD player will bypass all digital-to-analog decoding of the CD, including the HDCD decoding.  As such, the only way to gain the benefits of HDCD when connecting digitally is if the receiver/processor/DAC you are connecting to includes HDCD decoding.  Rotel’s RSP-1066 and RSP-1098 Processors, and RSX-1055 and RSX-1065 receivers do include HDCD decoding. Otherwise, the only way to get the benefit of HDCD is via the analog RCA connections.