im running oem m-parallels and the fronts are 18x8 et 13, the rears are 18x9.5 et 25 with the same tires you posted.
Im no expert but I would think that 1mm would not make a whole lot of diff.
there is an oem e38 set on ebay right now, but its already at 1,000 bucks and there is still 5 days left.
darron