Does anyone know where I would be able to find large dummy loads?
I've recently received an oscilloscope and would like to start setting up my amps with it.
But in order for me to do it correctly, I need rather large resistors.
I haven't been able to find any.

Heck anyone know and surplus electronics stores in the GTA?

 

parts express has 25 watt and I think 100 watt wire wound resistors.... you should be fine with the 25 watt ones submerged in distilled water or oil.....