I guess you have already checked out the sport line springs. Yes they will give the biggest drop and the car will look sweet, BUT dont forget to check the camber after the drop and fix it if u need it. The back will mostlikly need it. Yes you will be able to use them with the 18's, it just depends on what size tire you use with them. 225-40's should work fine but always check for any rubing, all cars are different and accecpt mods differently even if they are the same exact model car and year.

dfresh