You say that... But it should just play it back as a bitstream via your optical output, if you have one. You just need to make sure that QuickTime is not altering the sound in any way. You can do this in iTunes by making sure that the volume control is set to full, there are no volume or EQ adjustments and all sound check/cross-fade options are turned off.
As for DVD Player, I haven't tried that option yet. However VLC will play DVDs so I assume it will also output DTS for you.