So I put on the 96643C OEM style locks today. I have the 20" Midnight Silver RS package wheels. I think they look great!
In case it helps anyone else in their decision, I've attached a couple of photos showing how the polished chrome OEM style locks look on the Midnight Silver rims. Obviously, the locks are not Midnight Silver, so no, they don't match the paint on the wheels, but to me, they do absolutely look like they belong on the rims. The hub cover is not Midnight Silver, it's satin chrome with polished chrome accents, so the polished chrome locks look like part of that scheme.
If anyone would like better photos, PM me, I'll see what I can do.