Some of the older Denons were built on panasonic architechture. The Denon 900 shared alot of technology w/ the Panasonic RP62 while the Denon 1600 shared w/ the Panasonic RP82. The Denon 4800 was also a 5disc player built on the RP91. The 1600 and 4800 both added better DACs and Bass Management for DVD-A. Since then I beleive the technology sharing has stopped, especially since Panasonic went to an in house all-in-one mpeg decode & deinterlacing chip. Panasonic finally came back to the Faroudja deinterlacer w/ the upcomming S97 scaling HDMI player. I don't think it shares any technology w/ the current Denons, but I could be wrong.
This is interesting, as I bought the DV6400 because I found it had better audio than the Denon 2200 and almost as good as the 2900. Moreover, here in Canada, the Marantz retails for 400$ and 1000$ less than the respective Denon models (which also aided my decision). The 1400 is not available on this side of the Atlantic, or I'd have considered it.