Multi-Audio Channel compatible video compression

I currently use Bink (RadTools) to compress video for game development and I'm usually not to happy with the results. I've been looking into Divx or WebM in order to conduct some testing but run into a wall when dealing with the number of audio tracks I need in order to run 5.1 with localization (Currently 27 tracks, swapping L-R-C with different languages). I believe Vorbis and AAC both can handle a good number of tracks but I have yet to find an encoder that will allow me to add anything more than 6 (5.1). After encoding, the game engine must also be able to select and play certain tracks in different combinations. Is there another solution (legal and able to be licensed) or am I stuck with Bink.

Joe Wilson