FYI you might find other ways to do this using a digital route with HQplayer, that is very well coupled with Roon: https://www.signalyst.com/consumer.html
Here is an extract of the manual that you can find (HQplayer-manual.pdf) on this site. I did not experience with it but it may open a full route for processing multichannel audio in a flexible yet consistent, modern way - it already does extremely well with two channels, using Roon as front end.
Good luck in your investigation. In a previous system I was using a modified Pioneer DVD reader with digital 5.1 outputs, on three Tact 2150 amps (similar to Lyngdorf). It saved me from needing an expensive multichannel preamplifier and had all required flexibility. Your goal is different, like “augmented stereo” as it seems. Maybe HQplayer can perform this, in a RAAT-compliant way.
HQplayer manual extract:
Number of output channels can be chosen from “Channels” selection, possible choices are “2” for stereo, “5.1” for normal multichannel, “7.1” for extended multichannel and “16”/”32” primarily for complex matrix processing cases.
DSD content can be transferred to the audio device by packing it into suitable PCM container, select “DoP” to use the DoP v1.1 standard. The “2wire” setting enables dual-wire channel bonding to achieve 2x higher sampling rates for both PCM and DoP-based DSD on those DACs that support this feature. For ASIO on Windows, “AltDSD” changes units of the DSD sample from bit to a byte, use this only when experiencing incorrect DSD playback, incorrectly enabling this will make the application crash (currently known devices to need this setting are Playback Designs and Merging).
Channel mapping is following (regardless of driver type):
0. Front Left
1. Front Right
2. Front Center
3. Low Frequency (LFE)
4. Back Left
5. Back Right
6. Side Left
7. Side Right