In my opinion, you only need a medium/light on the fronts and a bit darker in the back. Mine came that way and it helps A LOT. Any good tint will remove the UV and a lot of heat even if it is practically clear. Really dark back window tint might look cool, but try to back up at night....
Legality is important too... you never want any reason for the police to pull you over because they are curious....
Monaco Blue, ///
ZHP, ZPP, ZCW, Hard Top