GSX already supports fully 3d positional audio, since its first release. Each sound in GSX is not just coming from the "front" or "back" speakers, that would be far too crude. Each and every sound in GSX is FULLY positional, meaning it has an assigned 3D position in the world.
So, for example, passenger sounds DO come from a point in the cabin, the sound the catering cart does is coming exactly from were the catering vehicle is located, etc. And, of course, their position is compared at each frame against your eyepoint position and orientation, so the effect is entirely realistic.
In addition to that, some sounds are flagged as "cockpit" sounds, so they are represented to come from the cockpit or the captain headphones, without a definite position in the world.
Of course, in order to hear all of this, you must have a sound system capable of running positional audio correctly, like a 5.1 speaker system, or a 5.1/7.1 headphone.