I'm not sure you can find the Kahn wheels in the US.
18x8 may be a problem with a lowered car. You may have some offset problems. Most people use 18x7 or 18x7.5, I dont recall anyone ever using an 8" wheel. It may work with stock suspension, but I think on a lowered car the front will be a problem due to the suspension parts.
I've used 225/40/18's on 18x7 at one time. I had the car lowered about 1.7~1.8" and it rubbed a little bit on large bumps.
The following will not rub: (from everyone's experience)