I think 18" rims look good on S13's but to make it look even better IMO you need sides, f/r bumpers then 18's start to look smaller and the car balances out more....
Here a pic of mine for reference its rollin on stock G35c 18's with 225/40/18 all around with TEIN owering springs, still need to get coilovers so I can lower it some more:
