Mercedes and BMW put wider tyres on the rear of their more powerful cars than on the front and the electronics are tuned to these. I can't see the point of putting wider tyres on the rear of a modestly engined car, but any change constitutes a modification and may be penalised by your insurer. Michelin Primacy 3s or Pilot Sport 3s of the same sizes as your existing tyres are probably your best bet. Unless the car automatically resets its steering angle sensor you may need to have it re-set.