Get the 2016 if you're comfortable with the AC it has. The 3.73 gears are great, sure you could swap gear in the new car, but that's extra work.
If you want 4.03 gear then you might as well look at the newer car, since you're committing to the change.
As long as it is a 16 or 17 you really...
I'd star with wheels and a wing of some sort. Lights go Mishimoto and get some Euro tails.
Beyond that, some stripes, a hood and fenders, or bumper and diffuser could help.
What you have to do is make and keep a theme. If you go multiple directions it is easy to tell and looks...