P I have looked at the Vorshlag rear GT500 upgrade and am considering that.
I like Vorshlag too but this is one area that you can get the exact thing elsewhere for quite a bit less money. Find an OEM repair parts website and search for the GT500 brackets there then pick up the correct rotors of your choice. I think prices have gone up a bit but I did mine for about $275. All you need are the brackets and rotors. Shipping from Vorshlag can get expensive too.