Sounds like you use your sub for your 2 channel already so it must be getting its signal from your preamp. And if I read your post correctly, you only have one digital input to your DAC, right?
Use the digital input at the DAC for the CD player (assuming it is separate from the BlueRay) and take the analog from the DAC to the preamp for 2 channel music.
For movies, use the HDMI to the monitor (it will be for video only) and use analog audio outs from the BlueRay to your preamp on another input source. I did this on my Oppo 83SE and configured the Oppo in set-up to only send video through the HDMI (in my case I sent the audio through a digital out to my 7.1 processor but it will also work to send to analog outs). You will have to set-up the BlueRay for 2 channel out and it will funnel the main channels, surround channels, and LFE signal through your L and R output.
(self-serving message begins ...) Uh, you could also buy an oppo 83SE or 93, or 95 and just use that for everything. I know someone who has a used Oppo 83SE they are selling. (self-serving message ended.)
Cheers,
David