You do realize that if you are going to run 15's and not slam the car, it's not going to look good regardless of how wide the rims are.
You have a 4cyl and look at your 15's, picture your car lowered an inch and a half or so....measure it out, and you will see that that is not enough of a drop to make such a small rim look good.
As suggested, the Suspension Review thread will help you in making a decision as far as that is concerned.