Sorry to hear that but it's good that the N200 and the amp were spared . I have both systems isolated with fiber optic media converters. I also did it to combat noise , I never thought about stuff getting fried via Ethernet.
Hopefully your post will save someone that nightmare. It's cheap to do, in my main system I have a TP Link gigabit switch with 2 SFP ports one going to a TP media converter . The second system uses a TP Link media converter on each end. Cheap insurance and absolutely dead quiet digital