ok. good news is it's totally stabilized, convincingly, and i'm certain it could stay like that if i left it that way. sounds just like through the laptop - clean drivers, stable, no ambiguity.

bad news is that means there's a conflict somewhere, because i turned off every single sound-related driver and reinstalled the mixer drivers to get to that point.

i'm hoping it's the line6 drivers, because there was already a known issue with them. but, what i'm going to have to do now is turn each driver on one by one and see where it breaks. it might even break twice, who knows.