Sounds like most people defending 550 and putting down 540 are trying to justify their purchase. No need as both are very good cars. Maybe serve different masters. The 550 is raw power and the same size and looks as M5 for those questioning the motor in a 5 series. The 540 is a powerful luxury sedan. I have a 540ixM with Merino leather so price wasn't the determining factor. The 540 had the power and handling I wanted and personally I think the BMW inline 6 will outlast their 8 cylinders. I tend to keep my cars for a long time. Stop fighting 5 series owners, pick on the 3 series owners