Nah, it's only the very early Boxsters (97-99, pre -S) that can't handle 18s or 19s. By 2001, changes were made so that 18s were a factory option, and 19s should be no problem, structurally-speaking.
Personally, I would go with the BBS...as an OEM supplier to Porsche, I would approve of them more than I would the lobster claws, because the lobster claws are 987 and 997 wheels. It would bother me to see newer wheels on an older car, in other words. The LMs date from when your car was made...I know, because I saw a black Boxster in my parking garage with them in 2000 or 2001, and I have been in love with that look ever since!
Two things about the LMs...the price you are quoting seems quite low to me, at least for new wheels. Make sure you are buying genuine BBS wheels, there are quite a few low-priced clones out there. Second, if you can afford real LMs, you should also look at the LM-Rs...they are lighter with their back-milled spokes, and there are fewer spokes to clean.
