Hate to say it but have you looked at used C63's? With the C63 you would get a practical family car that isn't as big/boaty as your Challenger but has the torque you won't find in an M3.
2012 991 C2S
Still have BMW's in the family:
2003 E39 M5, 2009 F01 750i, 2010 E92 335i