Engine mods to 2004 Toyota Celica GT

Hi guys,

I know you must get these types of questions a lot but i'll ask anyway: i bought a 2004 celica GT that has 80,000 on it and am interested in putting money into it to make the car primarily more efficient, but also with some extra kick. I have researched a lot into Intakes and i think the Injen IS series ram Intake is going to be my choice, although i'm still on the fence of getting an AEM ram Intake (i'm more interested in low end torque). Since i'm improving my Intake i wanted to also improve my exhaust system i.e. new headers (DC sport?). Would it be more efficient to get a new exhaust (and if so, how much of the exhaust system)? I plan on spending around 500 total for the upgrades. Basically what i'm asking is, is it worth it for me to put this much money into a 10 year old car? If so, am i thinking of the proper upgrades/manufacturers? Thanks in advance