The JL gain setting tutorial tells you how to ajust for a specific power output, knowing the load that will be used. There are a couple of details that need to be understood.
First, the sub(s) must be able to handle that much power in whatever enclosure they're in. (duh).
Second, if you adjust with the EQ flat then any boost, eq, or loudness added later could cause the amp to exceed what you set it for. The sub(s) must be able to handle that too.. (also duh).
The risk here is that the amp will clip when bass boost is added. That's where the scope is handy. Set everything up the way the tutorial says. Then hook up the sub and play some real music. Adjust your eq for what sounds good in terms of system overall tonal balance or whatever floats your boat. Watch the scope as you turn up the volume and make sure it doesn't clip.