Personally, don't run all seasons. Run summer tires for summer and run winter tires for winter.
Do the M6 reps. Have you seen the new time attack versions? They are hot right now, and even lighter than our current standard silver/gunmetal finish M6 reps.
What I would do, given I have the space/etc, is keep your stock wheels and run winter tires on them. Get the M6 or whatever other wheel you like, and run summer tires on those.
The RE050A are very good tires, and you will like them a lot, imo
XI does not change too much, you can run staggered wheels just fine. We have sold a bunch of staggered set ups to XI guys without problems. A search will only reinforce that statement.
Let me know if you have any other questions!
thanks.
-Don