Texas, I'va done my homeworks and trust me, I know my shit about 8th gen SI. (and honda in general). I had a 2.25" dropped integra before the SI and yes, it looked awsome!
But because of the slope in my driveway and the fact I work on civil construction project, having a 3" clearance gap makes no sense at all.
18" are 8" wide so I would need 225/40 if I want it too look good. And that gives about the same "tire height" but will have harder sidwalls so the ride will be "less comfortable".
ohh and spending 1600$ on a set of cheap ass tenzo wheels + tires makes no sense at all. (I could keep the oem 215/45/17 if I go with 17")
But all in all, I agree, 18" + slammed WOULD look better.