OKL those are in fact the lightest Porsche wheels on the market atm. They are everywhere flashing on the aftermarket wheel websites and shops locally. I actually love the black version of those.
DOT is cracking down badly on aftermarket wheels here recently so the price is nearly half of what you are paying the states
. Needless to add that I need to borrow my mate's Cayman wheels each year to pass annual inspection :/
RE rigidity, well they are cast wheels. Perfect for normal operation if you ask me but don't expect that they have been xrayed, QCed nor visually inspected before being passed on to you. Based on luck mate
That said, if you have a family, I'd say pass brother
Get an aftermarket wheel from a specialized wheel manufacturer. Saying that... mine are so brittle (forged aluminum) something tells me that the cast wheels you are looking at now are far superior rigidity-wise lollll