This will take care of DVD player. You'll get video on the HDTV and surround audio from your speakers (mute or turn down TV speakers). Since the audio is digital coming from the player optical = coax = HDMI (if it were available).
DVP-NC85H (HDMI OUT) >> HDMI cable >> STR-DG800 (HDMI DVD IN)
DVP-NC85H (DIGITAL OUT COAXIAL) >> Digital Audio Cable (Coax) >> STR-DG800 (DIGITAL DVD IN COAX)
STR-DG800 (HDMI MONITOR OUT) >> HDMI cable >> SXDR KDS-60A2020 (HDMI IN)
For your HD cable set top box (STB) with HDMI OUT, add the following.
STB (HDMI OUT) >> HDMI cable >> STR-DG800 (HDMI TV/SAT IN)
STB (DIGITAL OUT OPTICAL) >> Digital Audio Cable (OPTICAL) >> STR-DG800 (DIGITAL TV/SAT IN OPTICAL)
With this overall set-up, select the correct HDMI INPUT on the HDTV and from then on you can switch between sources (audio and video from DVD player or STB) using the STR-DG800's remote.
BTW, I only suggested the audio coax and optical connections to take advantage of the default set up of the STR-DG800 - simpler.