Black is a better match IMO although you might notice more brake dust, compared to gun metal. I was really happy with my gun metal rims not showing brake dust but then, my Corvette was Blade Silver so gun metal went well with that silver colour.
That's a tough call Cariboocreek. Perhaps a plain semi gloss black? Powder coating companies usually will carry colors swatches. Tape a few to your car and see the type of contrast the various blacks have against your cars body color.....Good luck.
My vote would be to stay with the gunmetal. I like a little contrast. With the black on black, the wheels tend to go unnoticed. Now if you're going for the total blackout look, that's different. I had competition grey on my red c6 and really liked that look.
Although a good friend's choice would also be all black,
I also am more partial to the chrome with black appeal.
Realizing it is not everyone's choice ... but I do not mind being a black sheep. LoL