Are we factoring in manual vs. auto trannies here? I think that smoltz' and Jussi's answers sound about right with the audis systems losing the power that it loses. I know that AWD/4WD vehicles lose an enormous amount of power and if thats also in an automatic car, thats even more power lost. I would guess that an auto awd audi would lose between 20-30% depending on the drivetrain. And a rwd manual bmw, losing less that 10% (HP)
Just my two cents.