I'll second the suggestion that you post your questions on AVS. Lots of knowledgable folks there.
You cannot get true high definition from any current DVD player. What you can get are DVD players that will scale standard definition 480i sources to high definition resolutions like 720p or 1080i. DVD players that offer that sort of scaling generally will only do so over a digital connection like DVI or HDMI. I believe that the two Denon DVD players that you mentioned have both DVI and HDMI outputs.
Looking over the manual that you linked, it does not appear that this projector has HDMI inputs. The 6000 model does appear to have a DVI connection, but from what I gather it is used only for purposes of stacking two or more projectors. It does not look like you can use the DVI connection for the output from a DVD player. If that is the case, then you'll be limited to using the component outputs of your DVD player. In the case of those two Denons, component output is limited to either 480i or 480p.
The native resolution of the panel used in that projector is 1280X 1024, so even if it had a DVI or HDMI input, neither of those DVD players would be able to output the native rate and the projector would still have to scale.
That being the case, the best connection might be the optional SDI. With a suitably modified DVD player, you would be able to output 480i digitally to the projector, which could then scale and deinterlace without the need for a DA conversion. If the projector's internal video processing is not up to par, you could in the alternative look into an outboard scaler like the iScan or the Lumagen, either of which could take an SDI output from a DVD player and output your projector's native rate over an analog connection.
Good luck.
