Sweet ride!! I find the yellow E9x really stand out, there is another E9X M3 sedan though in the west coast - I believe Dakar Yellow? I for one actually prefer the I drive...mainly just for the dash, without it to me looks naked (which sometimes isn't a bad thing).
As for your exhaust question - Definitely an AA black edition exhaust will suite your need...low, bassy rumble. Most of the ones your listed aren't as low-bassy, or on the other hand can be too loud.
Anywho, amazing choice in colour. Enjoy in good health!