The Si has all those mounting holes, the regular sedans don't. I think the regular sedans also have the center brake light inside the rear glass, since there's no spoiler to carry it.
If you were looking to get a different spoiler, consider getting a lower trim level trunk lid- if there was one local to me that's what I would have done, that way you don't have to deal with covering the holes. Most of the aftermarket spoilers seem to be 3m tape stickon style, though. If you're talking about a big GT car style wing, that's a different story and you'll probably have to drill.
Looks like Seibon makes a few different hoods, check it out-