Depends how you want the wheel to look.
mine are 19x9 front 19x10 rear ET 20, which is IMO perfect, fills the archs but no rubbing.
if you went 8.5/9.5 id look for ET17 to fill it out, if 9.5/10.5 then go ET23, thiat way any of the 3 widths will sit similarly on the car.