Just borrowed a JCM900 head and Marshall 4x12 cab to record some death metal. This is the first time I use one of these and I don't wanna blow it up. I know you can switch between 100W and 50W, so I wanna use the latter since I don't need so much power. As far as connecting the cab, there are two inputs...one that says 4ohm input and another that reads 16ohm input. Which do I use? What are some good settings for that death metal tone? I'm looking for some good crunch and not so much of that mid-dy "chuga chuga" sound. Kinda like Black Dahlia Murder.