Scored a VP-50 Pro from a Goodwill auction the other day, being shipped here now. When it gets here, I'll be connecting a Pioneer CLD-97 to it, and outputting it to a Denon AVR-E400 receiver, which has a ADV8003 video processor in it. I know the VP-50 Pro only has a 2D comb filter in it, and I know earlier ADV chips (e.g. ADV7842) have a 3D comb filter in them, but looking at this datasheet, I cannot tell if the 8003 does or not.

I guess my question is whether or not I should be outputting 480p (or 960p) from the VP-50 pro to the receiver and letting that handle upscaling/3:2 pulldown the rest of the way to 1080p, or if I should be doing more in the VP-50 before sending it to the ADV8003. Basically - what do you think each device should be doing to maximize the video quality I'm seeing come into the display?

I had a look at the service manual for you for the Denon AVR-E400, I think there was a chip you missed. The composite signal goes through the ADV7850 if you look at the block diagram. The ADV8003 seems to manage HDMI inputs and other digital things, so isn't to do with the composite signal. My Advice would probably be to use the Denon to do the Comb filtering first since that has a 3D comb filter and try and see if there is a pass-through setting on the Denon for resolution or set it to 480p or 480i. From there you can input into the VP-50 Pro and use that for upscaling. I think it's one of those things that you should experiment with, try using the Denon to upscale or deinterlace and then try using the VP-50 to deinterlace and see which looks better.