Help with Meridian 598 DP

I just bought the new Steely Dan "Gaucho" DVD-A disc (my first DVD-A disc). I am feeding the Meridian 598 signal out of its auxillary digital output via S/PDIF to a dCS Purcell upsampler, then into and Elgar D/A converter. This is a two channel setup.

My problem: I cannot get the disc to play in stereo. When I select the stereo option on the disc menu, I get "no input" on the Purcell. If I play it in "surround sound" mode, the Purcell picks up a signal, but I only get 2 of the 6 channels, so backgroud vocals and horns sound far away.

I have gone over the manual several times and tried just about everything I can think of, but still no stereo.

Any suggestions?

Thanks,
Dave