I vote stay chrome. I am a big fan of the gloss black but on a black car it gets washed out and makes the front look empty, only looks good with a contrasting colour. The e63 has the droopy eyelid grills which I never really liked. I do think a subtle M6 badge on the slats would be nice like here http://lln3.mnmcdn.com/cars/bmw/big-...upe-38_653.jpg
Another idea is to have the slats black but the frame in chrome....that is the best of both worlds, I have seen people wrap the slats. The text at the bottom of the reg surrounds is fussy IMHO (I had them on my M5 but I have since changed my mind). German font has been ruined for us all by the Audi and VW lads.
That being said an M6 is a special motor, your not tarting up a 630i to look like something else and you should have it as you like it. A totally blacked out M6 wheels, windows, grills etc can look awesome.