Would disconnecting the driver's indvidually work as a good way to figure out which driver is causing the noise? The system runs in parallel so loosing one driver just increases the resistance for the amp to drive which shouldn't cause any issues. It would be like having a sealed EP600, which is what the 800 is based on any way, IIRC.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70