I found a way, but it's not ideal. My PC has an HDMI output and a Display Port output. I use the Display Port to connect directly to the TV (no longer going into the MX121 first) for the picture and use the HDMI output to go to the MX121 for sound:
PC -> DVI -> TV
PC -> USB -> DAC -> RCA L/R -> MX121 (pure direct mode) -> Amps (can choose whatever input you want on the MX121 - you'll still get a picture on the TV as the PC is connected directly to the TV)
CD -> Optical -> DAC -> RCA L/R -> MX121 (pure direct mode)
PC -> HDMI -> MX121 -> Amps for Dolby True HD, DTS-HD, etc. (the video is simply "swallowed" by the MX121 as it isn't outputting a video signal anymore)
There are a few disadvantages with this setup. If you have another device such as an XBOX, you'll need to use some form of HDMI splitter to use the TV and will need to send the sound to the MX121 via an optical output.
Last edited by darcraver; 04-24-2017 at 10:12 PM.