I'd get an M4 or C63.
I have a facelift 6.2 C63 and its a beast. It's mapped, uprated Quaife diff and secondry cat deletes. Making circa 500
A stock car makes 457, perf pck car 487 then u have the 507 edition. Locking diff is rare option.
Be prepared for silly service costs and crazy low mpg.
Personally new M3 is very appealing. Quite like the 4 door.