I have no SPDIF at the moment.
I have a Terratec EWS 64 XL under my bed with SPDIF,
but it is ISA-slot based!
Ask your Grandfather what ISA was!
But I have another idea for you based on my own setup:
Do not use Aureon with MME in Voicemeeter!
Instead use your Realtek with WDM for low latency.
Select WDM Realtek Speakers in Volumouse.
Use your Aureon with its ASIO driver and connect Realtek HD Output with the input of the Aureon.
This idea is based on my own setup:
I still like to use the old SRS Audio Sandbox especially for TV and movies.
But I also like to play VST instruments at the same time.
The SRS Audio Sandbox does not support (of course) ASIO or any virtual audio driver.
So, I use a workaround:
I use ASIO4all as A1 (256 samples at 48 KHz) and set WDM latency to 160 to get ultra low 80 samples input latency in swift mode for physical audio input in Voicemeeter.
ASIO4all uses Realtek HD Output WDM only.
Volumouse could control Realtek Speakers Output, but I prefer to use SRS Audio Sandbox (WDM).
In Voicemeeter A2 uses KS: SRS Audio Sandbox.
KS is set to 256 samples in Voicemeeter system settings.
SRS Audio Sandbox uses NVIDIA High Definition Audio (HDMI) as output.
I physically connect my LG monitor's audio output with Realtek HD input (hardware input in Voicemeeter!).
I know that it is some kind of resampling-orgy including quality lost.
And of course it is limited to stereo (no native surround).
A2 in Voicemeeter uses "Up Mix TV" option to feed fake surround to SRS KS input.
SRS Audio Sandbox operates in stereo mode with TruSurround®XT on (emulating virtual surround with stereo speakers).
What a mess?
Yes, it is.
But seriously, I do not care, because I can change volume for video and audio playing content rapidely with Volumouse, while at the same time I can play and record VST instruments with low latency.
I know it is a very special (unique?) setup, but I have no plans to win an award for superb audio engineering for it.