v_therussian

9inch wide rims with ET40 offsets should work on X-drive cars. Obviously, if you're running 20 inchers, you'll hardly have to worry about any issues clearing the brakes, but you might have some rubbing on the inside - which should be easy to fix with some small spacers. Again, this is all just rough guesstimates without knowing exactly what car and rims we're talking about.

PS Xi e60's have a LOT of room in the back. It has been proven by several members on here that you indeed can run a staggered setup on Xi as long as the overall rolling diameter of your front wheels is not more than a couple of mm within that of the rears. Therefore, if you choose to go with a staggered setup on Xi, you not only can, but IMHO should get rims with a more aggressive offset in the rear. I'd go for something in the 32-35mm range for the rear offsets. But again, just about each case is unique, so I highly recommend that you post your exact car, any suspension mods (dropped or stock height?) and the exact rims you are looking at - this way you'll get the most accurate response.