Denon AVR-5805 Original Version
I have the original Denon AVR-5805. I am not sure to all of the differences but I know that the MK-II version will pass a full 1080P video and also gives you your onscreen display via the HDMI. My 5805 will only pass ether a 720p or 1080i and the onscreen display is via component, S-video, or composite. If you check the Denon web site all the differences are listed via a pdf download.