Prepare 3D Audio Mixer Options

Hi everyone, after some time using P3D I have decided to look into the audio options in order to separate some of the sounds in a more realistic way. However, the only options available are the four volumes (Engine, Cockpit, Environment, Voice) with no way to separate any of the first three outputs from each other. The Idea is to obtain the engines sound coming from the main speakers (with bass Sub) and the cabin sound from a more modest output situated the above overhead panel so to emulate the cockpit ambiance. Again in the audio mixer, one can only isolate Voice Capture (mostly not used as we tend to rely on FS2crew and external ATC) "Voice  Playback" and "Primary Playback" this last one being where all the internal and external sounds seem to be directed to (the device can be chosen) but never into separate ways. Is there anything else that can be done for this separation or does it mean software mods?

Thanks