I would be surprised if it turned out to be this high but I do feel that making the S6 compete with the 550i and e550 will be a mistake, in general the S-Line competes with BMW's M/Sport and Mercedes' Sport versions, the S has always stood separate from these and in my opinion should remain so.
I stick by my guns in saying that the S6 will have 435-440hp, either officially or unofficially.