OK, so I went further to actually read the manual for your receiver and the D-dock. The cable you found for $2.26 does exactly the same thing as Denon's $129 dock.

I was just used to how Pioneer handles iPod integration, actually accessing the digital files, but Denon's docks compatible with your receiver are analog only.

Pioneer PDP-5020FD, Marantz SR6011
Axiom M5HP, VP160HP, QS8
Sony PS4, surround backs
-Chris