Realistically, the benefit of running a wider wheel on the back of an all wheel drive vehicle is minimal at best. Staggered setup is used on rear wheel drive to give an added contact patch for grip on the drive wheels, in an xdrive setup you have almost twice as much contact patch for acceleration grip. If you are going for stance, you are better off with spacers since you will:
-spend less on tires
-run more all season type tires
-be able to rotate your tires if you have uneven wear patterns
-not have to worry about overall diameter differences
I'm not damning the practice, it just seems like a big investment and a lot of hassle for very little return. As Azn_ignite said, 275/30 and 235/35s are the closest setup, but between the sizes you listed 265s would match better than 255s.