He could be all show and no go guys.
However 18s will have small side walls and you will have to watch out for and aviod pot holes. I doubt you want to bend a 18" rim right after buying the thing. Get 17s and lower it.
Friend of mine wants to put 17" Motegi MR-7s (played out and out dated) on his 240sx and not lower it. Hopefully he'll see the light after he see that it looks like ****.