I recently purchased G spiders for my SC430 from a Lexus dealer on another forum - club lexus. Sewell is having a promotion.
I looked at quite a few aftermarket wheels, and mainly due to wheels for this car are hub-centric, not lug centric, pushed me towards the OEM wheels. That and the TPMS. Once you start asking the aftermarket folks questions concerning those 2 things, you get answers like, "uhhhhh, I don't know"