Jambient. Dug into the specs for Jambient a little. While cool, it will not do what I want for Halloween. It does let you place multiple sound sources in a 3d space and dynamically move them around. It only supports two stereo speakers tho. There is reference on the site to supporting quad speakers with DirectX8, but I want something that could support an arbitrary number of speakers. Also I think Jambient assumes a single listener at a single location and that is not really what I want. In practice the effect may be the same but my design assumption is multiple listeners in multiple locations, where the dominant sound at that location is the local sound effect (say my graveyard noises) with the occasional mix in of a panning sound (a ghost flying by). I think I need to talk to an audio engineer to really lay out my specs precisely.
Also Jambient is really designed for realtime usage by an operator, I need full scripted/programmatic control based on events.