That would be a great place to start on the rears.
I'm currently running 19x9 ET48 with a 20mm spacer (effectively ET28) and it just barely pokes outside the front fender. When I was running the 10mm spacer in front (effectively ET38), the wheel barrel would rub a little on the coilover spring under full-lock of the steering wheel. I would go for ET35 or lower in front if you are doing a 9" width. The front fenders on an E46 have lots of room. It's the rear fenders that seem to be lacking space.