I was playing around on the TireRack site and noted this fitment for an e60 550.
BBS RGR in Diamond Black
09.0 x 19 et20 20.8 lbs
10.0 x 19 et25 22.0 lbs
These are forged lightweight wheels. Note that the price is $4500. The centerbore is the same size as the M3, also.
These are my favorite BBS wheels, but I think the RAC group buy is a superior purchase.