2012 Kia Forte with XXR 530

Your best bet is the widest 18 you can go if you want to stick with 18s, which is 8.75 without worrying about offset on a 9 inch. Lowest offset you can go without rubbing is around +30 on an 8.75, XXR comes in weird offsets (mine is +33 :s). You can stretch the tire, or get thinner tires to go lower or both. If I were to lower mine more I'd definitely need around a 215 ish tire. i'm sure others will chime in on their setups, there are definitely some really clean slammed Fortes with excellent wheel setups here!
If you do like a 215 on an 8.75 rim you'd be able to slam it pretty hard I think

here's a 225 on an 8.75.