Actually, I'm pretty sure on the earlier 1050s, switching to 6.1 when playing a 5.1 source WOULD knock off the sound (he has a 5.0 speaker system, BTW). I remember Outlaw putting out a bug report on some 6.1 oddities, though I don't remember if it was fixed in later production runs.

Still unresolved, so lets keep the (much appreciated) ideas flowing!