If your system will stay this way then you will just keep listening to standard DD/DTS.

A HD621 will bring simplicity with 6 HDMI inputs and switching controlled by the Meridian remote.
Next, audio quality will improve via HDMI as your Oppo decodes the new Lossless movie and concert formats.
Also i've found that the HD621 is excellent at driving 15m HDMI lengths. It seems to have a much better output than standard HDMI sources.

If you for example want a third HDMI source you are out of luck without the HD621.

Also with the new 3D update it was kept up to date and the audio signal detection was improved which I noticed with some misbehaving material. I don't have anything bad to say about it actually and that is unusual in the HDMI world.

DSP8000SE, DSP7200SEHC, DSP5200SE sides, DSP7200SE rears, 861v8, 210, Sim2 Ultranero 4, Stewart Cinecurve 2.35:1, XEIT CM-5E Anamorphic lens, Dune HD Duo Cinema 8K and Wireworld Platinum 48G HDMI -> UHD722 -> Shunyata Omega Ethernet. Shunyata/Furutech power-cables/filters. SR Master Fuse@861v8. Uptone Etherregen with 10MHz OCXO clock.