Finished reading the SRS web site, and this would indeed do pretty much everything I want. SRS does the stereo field calculation and corrects for the omnidirectional nature of the microphones and so forth, and Focus realigns speakers not facing toward the listener - for example, in cars - to bring stereo images up to head height.

I'm currently finding out more from them about implementations and licensing issues. If someone else has done the maths then I'll just buy the end product.

I can see this would make tanstaafl's dream.

Save the whales. Feed the hungry. Free the mallocs.