That's a good question. I'm not sure if BBS make wheels for Porsche.
I would think at this point Porsche make all their own wheels, even the Sport Classics which have the traditional BBS mesh look.
BBS wheels are nice because you can sell them on Ebay to other Boxster owners!
I got a nice used set of BBS RK's for my old car for about 40% of the new price.
Check the Porsch CLub in your country. Here in America the Porsche CLub classifieds are a pretty good source for parts.