People!!! Why are you all complicating this and confusing the OP? The solution is rather simple. Connect the Node with Toslink to the Denon. It WILL go to the highest sampling rate the Denon allows for optical. NO need for DAC in between the Node and Denon. It will use the Denon's DAC. You won't be listening to the Node's DAC even if it were a POS.
And the whole "pure direct mode" thing only matters IF you are using analog inputs to the Denon, in which case the DAC in the source component WILL matter. If NOT using "pure direct", analog input signals will eventually end up thru the Denon's DAC anyway.