NICE car -- fwiw, a number of folks on this forum opine that, unless you're actively racing your car, a strut brace is not going to provide any discernible improvement to handling. See, e.g.
http://forums.pelicanparts.com/porsche-911-technical-forum/847260-strut-tower-brace-has-better-clearance.html
You might want to start with shocks/bushings?