There is a way to do what you are asking for using the AVR-3808 internet radio facility.
Lets say you have your slimserver on a pc with ip 192.168.o.5
Then you need to go to this site: www.radiodenon.com and add this as a station like this; [Link: 192.168.0.5]
after that you can select that in your denon under internet radio and added stations.
Slimserver thinks that it is streaming to a winamp software player and Denon think it listens to a internet radiostation.
The down side is that it only works with mp3.
Maybe someone else has done this in a better way, then please let us know.