Just got the S4 cab brochure and its a bit fat! [the car that is, the brochure is the usual arty crAp, only one picture with the roof up and none of the rear seat] .
It weighs 1855kg in 'wet' form with no driver (68kg) and 'handbag' (7kg). My Avant is 1720kg and the Saloon 1660kg, so with two less doors, the Cab is 195kg heavier than the Saloon! Even without 4WD, my, bigger, CLK500 cab looks a lightweight at 1710kg and that's carrying Mercedes usual excess weight!
Also, look at the S4's 0-100kph times:
-Avant, add 60kg and the time is up 0.2s to 5.8s
-S4 cab, add an extra 135kg but only 0.1s is added to give 5.9s. It does'nt make sense does it? Either the Cab is'nt that fast or the other two are faster than stated...