i remember starting a similar thread on this a while back (not exactly sure if i did it on this site or some other site). being the cheapskate that i am, tried it out with the following gear:
setup 1:
HP MP200 media player --digital coax cable--> Denon DAP2500a DAC
setup 2:
(generic) Pioneer DVD Player --digital coax cable--> Denon DAP2500a DAC
* media: FLAC files for the media player and an audio CD from the same FLAC files
the result was as expected. my generic DVD player sounded way better than the multi media player in all aspects.