Is anybody paying attention to the question? he's asking the thread size of the screws, not the size of the speaker and if it will line up.
And the answer is that the threading doesn't matter, get a slightly larger screw so it will hold tightly, but it's possible that the new speakers won't even line up the current holes, and if that's the case then the current threading matters even less because he won't be using the stock holes.
I already said that in the first reply, its just funny how people are so quick to jump in when the question has already been answered and without even reading the question.