I was wondering what I should replace in my 2002 Subaru Wrx Impreza Sedan

it has 145,000 miles, an exaust leak, and in January had a tranmission rebuild and the 2,3, and 5 were replaced. I'd like 300 - 350 Horsepower and it's at about 227 Stock. We bought New Pistons, Header, Intake, and a Blow - off Valve. What I'm looking to pay is about $2,500. It might not be enough but if posibble make a prediction of what I could do.