The current draw on a very high powered amp (and if you're shopping for seperates, you're shopping for power) can suck all of the juice from a 15amp fuse. If you've ever run a blender and the hot-plate at the same time and everything in your kitchen died, you know what can happen.
You'll want to budget-in a qualified electrician adding a seperate outlet, on its own fuse, just for the amp. This could be a wise idea for some super-subwoofers, with their "2000watts peak" amp driving multiple 12-15" drivers.