The 18 inch BMW performance rims should fit if you get all rears.

 

I think my 166 reps are just fine on my xi.

 

I have Style 128's I'm selling, just got new set of wheels. 10mm spacers on the front with a 46 offset (bringing it to 36 after spacers) and 51 offset in the rear with 15 mm (bringing it to 36) 19x8.5 front and 19x9 in the rear. I love this staggered set up and is a great looking set for the XI's. Will work on your car.

M5 wheels are hot but lets be honest, you DONT have an M5. I have a 535 with 550 kit now, dont want 550 wheels cause they wont fit mainly and I dont want to look like a 550i! lol anyway check em out there pretty nice. I tested fitted m5 wheels on a XI and it wasn't happening.

Mine are OEM btw