Correction: The DAC is a Theta Pro Prime II not a Basic II. Same questions apply.
You would have to use both Toslink and Coax output on your DVD player, one to the Pro Prime II and one to the Casablanca. The Coax output should sound better. What I'd do however is sell off the Pro PrimeII and use the DAC's in the Casablanca for both music and Movies, but listen to both and let your ears be the judge. I think the DAC's in the Casablanca are much newer and should out do the Pro Prime II. A dedicated transport for music or better yet, a stand alone CD player would be nice for 2 channel music.
Set player output to bitstream to disable it's processors. Hook 5.1 analog cables to pre/pro for music surround, hook digital cable from player to pre/pro so that pre/pro can decode movies, hook your other degital cable from player to your dac for redbook cd and your dac's analog outs to cd inputs on your pre/pro. Switch inputs on pre/pro to match your source as needed.