Adaptive audio / channel switching

First off, I'm a sound designer / composer who dabbles in programming, not the other way around. For most of my projects, I have an actual programmer, so that's not going to be an issue, though, just realize that I'm not as code savvy as I probably should be.

I've looked through the questions and forums a bit for this, and I've come up wanting.

The general solution for adaptive music is to start two music tracks simultaneously and hope that the buffering is in your favor and they don't get out of sync too far. Even with a fixed update, that seems to be the case.

I've had some luck with fmod designer in creating multi-channel music (let's say 4 channels... two different L/R mixes), and fading between channels 1&2 (L/R 1) to channels 3&4 (L/R 2).

I've read conflicting things about the current state of Unity's audio engine -- it's a streamlined fmod in one thread, it's OpenAL in another -- and I've even read that full-fledged fmod will work in Unity Indie, and may even work with the outdated FMODUnity plugin from SquareTriangle.

If the last part is true, great... I'll just build an fmod library and work it out with my programmer. If not, is there a way (without adjusting the listener in 3D space) to change what's going to the speakers from L/R 1 to L/R 2?