For me, from a distance, the black wheels remind me of folks who lose a hubcap and don't replace them
Like you mentioned, it looks dull and dark. If there is a polished lip, that helps but otherwise, the tire and the rim become one. Personally, I like silver, especially on a blue car, of course that is what I have
Take a look at this thread for lots of ideas:
Post Pics. Boxsters with Rims.