Quoted from VolunteerPin:Thanks!
When I've looked at the other "S"s around, I can say definitively that the 2 best upgrades are tint (which I believe on all vehicles) and the upgraded rim size/color. The wheels are actually a dark grey which accents the silver very nicely. I also like the powder coated red brake calipers which breaks things up a little.
Fortunately, both can be done by owners on their own. The dark grey wheels do look pretty awesome, but cost of 21" performance tires would dissuade me.