alright, ohfara just asked me to post my thoughts.
i'm his partner in crime, it seems, and have actually had a bit of game time.
here's what i'm led to suspect:
some of the ark files are truly multi-channel ogg files; as evidenced by ohfara's findings.
the remaining ark files must be other portions of the game - i have no way (as of yet) to test this, but i'm thinking they're the programming for the stages, different modes, unlockables, and trophies.
anyone that's played the game for longer than an hour, please respond as to what the "


??" is in the extras section....