Ok here is my 2 cents: I have a set of powder coated wheels in the correct argent silver on my impala. While they will never rust I have a couple of issues with them. Along with the wheels and anything else as Gary mentioned powder coated items have a different sheen to them, so on the wheels it looks like a slight orange peel affect. powder coating them in black first is a great idea and then scuffing out side and spraying in argent sounds good to me. BUT hold on a sec!
Glass beading or sand blasting is a quick easy way, and IMO the easiest if you access to one, but please Note* the glass particles or sand will get stuck in the cracks of the wheel where they welded the inner piece to the outer rim of the wheel. If you do not clean this they will powder right over it, and it will look like CRAP. Take the extra time to take a razor blade or utility knife into those tight areas and pry all those little bits of sand and glass out. Then take some 200 and get it in there just to get the extra dust and dirt out. I am super picky, so I have found this works best so far, so when you do powder or paint it will look really good.
Unless you plan on driving in salt paint should work just fine.