Use line in for loud rock with your pre-amp/battery box.
example of what I use:
ca14 cards --> 9100 --> line in on 09hr and the gain on the 09hr around 40-50 and on the 9100 its about 12 or 1.
If I were to do ca14 cards --> 9100 --> mic in on 09hr I'm thinking it would be heavily distorted sounds.
the stuff about peaking is not complicated and quite frankly, just keep the two little bars from going to the extreme right of the monitor and you will be okay. You should expect it to rise when something like the drums are played but it will stay within a range and thats basically what you want to monitor.
try it out and you will learn from your mistakes.