Go for the black wheels - it'll look good. It'll have a visual match to the window surrounds, bumper strips etc. I would suggest a dark metallic grey or metallic black though. Makes the dirty a bit less obvious (so they don't look poo as you as you drive the car).
If you can get them done for £25 a corner with refurb that's worth a punt. I did mine myself and spent a fair amount paint, thinners etc etc etc. Probably the best part of £45 and I already had the compressor and airbrush (or rather my brother did ).
Could anyone please (last time i promise) Knock up a pic, using the sames pic as before, one where the spokes are black, and the lip is still silver. that would be great if anyone would.... thanks will be given!