Likely there arent right because GXP's have different size rotors and different part numbers for pads than what the amazon site may say.

Either you can go to a parts store and have them get you the correct factory matching rotors and pads or you can find the correct stuff online.

From some searching I did a little while back, the 2008 Buick Allure (lacross super) has the same size front rotors but arent drilled, so they should be cheaper.