No you wouldnt absolutely HAVE to. But if you can afford an SRT then why not? might as well grab an APEXi n1. its only 500 bucks on http://thmotorsports.com/apexi_integ...5/i-35731.aspx
Personally, i went with the Joe Z intake pipe and a drop in filter. the intake pipe is only $109 dollars of the ltuned site. and the drop in filter is another $50. its roughly a 5hp gain. compared to an SRT with race ecu which adds 22 hp and 22 pounds of torque. but youre spending 500 more dollars on the SRT. So i say get an exhaust. it adds more power and makes the car sound better and looks alot better than the stock exhaust. Maybe even get a toyomoto y-pipe? Good luck.