6.5.0-b9 https://github.com/mastercoms/mastercomfig/releases/tag/6.5.0-b9
I've started to document the sound effect cvars a bit better and it will improve in future betas as I do more testing on DSP effects. Hopefully this will lead to not only compatibility with surround sound systems like the ones you've been describing, but also greater overall quality of sounds and DSP effects.
If you'd like to know more about where the DSP values come from before I document them fully, you can check out the dsp_presets.txt file.