Yer the issue with tyre limitations in 16 will always be a pain. Jeez I did'nt know the Superlights were that heavy!
Oh well easy choice then, get custom wheels made up, about the $2000 mark or, buy Watanabes, at least $2500 or be patient and wait for a second hand set of wheels in the correct PCD and correct offset (might have to wait for a quite a while) and then the chance is 98% that the wheels would have to be modified to be wider for flares, more money!