I've got a 2005 CLS55, and I'm pretty sure the 55 is much faster than the M3 in a straight line. Doesn't come close in the corners though.
///M3 Mods: | Eisenmann Race Exhaust | Primary Cats Delete (TTP) | ESS Tune | 19" Advan RS | Eibach Springs | MS Air Filter | BMW Perf. Spoiler | BMW Perf. Splitters | Euro LCI Tail lights | Angel iBright v.3.0 | 20% Tint | Matte black Kidney Grills | CF Side Gills | Painted Reflectors | Black M3 emblem