Yep you want it on Auto, however, to the right of that there is a button for the "Rear" speakers, I think if you cycle by pushing you get various options like Matrix ON, Matrix Off, Off, On, etc... Also, if you click the Cinema button or Standard button you cycle back/forth from Dolby/DTS.

I would think that if you select DTS from the DVD menu, the receiver should recognize this, I need to test this soon, you've got me curious.

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85