Congrats on the new car man!
Have you stopped by the NASIOC GR fitment thread? There are guys running 265 width tires on 18x9.5" wheels at around 38-42 offsets. I know Mach V has pretty much the perfect wheels size on their site: 18x9.5/+42. If I had the cash to buy wheels and tires within reason I'd go with those and some 265 tires. No matter what you get over 9" wide you'll probably need some degree of roll depending on the offset, but I wouldn't go below about +38. I don't think you'll need much, if any, roll with 255's on a 9" wide tire at stock height.