@szuberi: AMG was acquired by daimler crysler few years back and works solely for mercedes now.
I said "AMG is for Merc as M-Tech is for BMW or Lexus for toyota" as in Performance and styling. For instance the M3/M5 for 3 and 5 series BMWs respectively. Both of the M models have more aerodynamic styling increased performance and much better road appearance.
Lexus does the same with Toyota Land cruiser or the Toyota Harrier.
In a nut shell the idea is to market the same product under different brand just to capture the entire market paradigm. Lexus has been overwhelmingly successful with it over the past few years. Lexus now is synonymous with performance, luxury,comfort expensive vehicles which was not always the case with Toyotas. Hence broadened potential customers.