Sorry, You never caught my question right. Regarding the new 3 audio channels which one will this play through
You said:
"Reason i ask is i want to assign a different wav sound"
So, what's relevance has which channel is used to play it. It's not something you can change by replacing the .wav file. It will play on the same channel the original sound from GSX played on.
So, if the reason of your further post was that you don't HEAR your new sound, is it possible you changed its format, for example using a Stereo file? The GSX sound engine is positional so, every sound source must be MONO, because it will be positioned on the sound field by the sound engine.