Did they come with the car when you bought it?
These 'carrera light' wheels from Porsche come in 2 set of sizes.
For 996 - 225/40/18, 8x18" front, 285/30/18, 10x18" rear
For Boxster - 225/40/18, 7.5x18" front, 265/35/18, 9x18" rear
If you have 265 rear tires then you should have the 9x18" rears. You can tell by looking at the tires if it's too narrow for the wheels.
I think they're _perrrfect_ on a Boxster without bodykit. I also agree that less is more and these 5 spokes look totally elegant. As you can tell I'm a big 5-spoke fan and my
last car also had nice clean stock 5 spoke wheels.
I also like BBS-style mesh wheels but I don't think they will look nice on a boxster without bodykit.