I recently did the same. I sold a 06 ZCP M3 and I needed a daily driver. So I brought a 640 GC.
Two completely different cars. The M can’t hold a candle to the build quality of the 6 series. At the same time, the 6 can’t hold a candle to the pure raw feel and driving enjoyment of the M.
But in all fairness, I miss that M3 everyday. But I’m not ready to give up the 640 just yet. This car just oozes sexiness.
Enjoy it brother
