I have Pioneer DV-676, Pioneer DV-400, GIEC HVD DVD player, Meck DVDP, and Liteon HDD/DVD recorder.

Of these, Pioneer has the best sound quality. The worst would be Meck. This is done by using the same source (LOTR Fellowship Of The Ring -Region 1 DVD).

I guess that Pioneer's 96Hz / 24bit Audio DAC is superior than the rest, which makes the difference.