I haven't done this personally, but there is a SWP BRZ around my area that I see from time to time that had the rear bumper and "mustache" paint-matched; I thought that it looked pretty good (sorry - no picture of it as I don't believe the individual is on the forum).
EDIT - found something similar on the internet - hopefully this picture helps you a bit; I think gloss black might look really nice, so be sure to share a pic if you do have that done!
