I'm not that excited by OEM rims: all 4 of mine are bent to some degree and my friend has had to replace both front rims on his Boxster.
There are some very high quality and lightweight rims out there, both forged and cast, from the likes of OZ Racing, HRE (costly though!), Vorsteiner, BBS etc etc.
I "stress tested" an OZ Racing SuperTurismo on my other car a couple of summers ago, and although I managed to bend all sorts of suspension arms, the rims themselves (when tested afterwards) were straight and true ...
Of course cheap knock offs are a stupid idea, and a lot of replicas are heavier than the originals, but you pay for what you get.