Well hold on there a sec. How did you figure out these won't fit? Check this out...
A 15x7 wheel with a +25 offset has a back spacing of 124mm.
I used to run a set of wheels with these specs on the front of one of my supras, no rubbing problems whatsoever.
A 16x8 wheel with 0 Offset has a front spacing of 111.7mm
Thats the size of the Compomotives that most people on the board are running on the front. Personally I think they stick out just a little too far, but they fit and don't rub.
A 18x9.5 with 20mm offset has an overall width of 261.5mms, a back spacing of 150mm, and a front spacing of 111.5mm.
So without spacers, the outsides are fine and will not rub. So the question is, is there another inch of room on the insides of the wheels? We know a backspacing of 125 is fine. I really can't remember what it looked like in there when I had those wheels on but I don't remember it being all that tight, those 18s MAY fit. If you could go to wherever they are and mount one on the car with the car jacked under the control arm, you could tell wether or not it would clear. Try turning the wheel both ways all the way and all. Maybe bring a 7mm spacer with you too. Obviously you'll have to use some judgement to determine if the rubber would clear. How low a profile can you get for 18s? If you could get one that was so low that the overall diameter is less then stock then you'd gain a few mms back on both sides. You don't have to go that wide with the rubber either, no more then a 245 for sure. I'm sure a 235 could be stretched onto a 9.5 as well.