04-06
Base: Single Exhaust, Single exhaust fascia, basic single cd sound system, usually cloth, generally hubcaps
GT: Dual Exhaust, HUD and 5 button dic options, Monsoon option, leather option, sunroof option
GTP: Supercharged, all options available

07-08
Base: Leather option, 5 button dic option, hubcaps or premium wheels, sunroof option
GT: Supercharged, all options available


Basically 07-08 had every option available on either model where as the Base models 04-06 were typically just rentals/ fleet vehicles.