Not knowing the stage packages, I took a look. The 2 says plugs, tune, 3.6, belt and a downpipe for the most part, right? The biggest increase you will find there is the removal of some torque management. TM is programming that attempts to keep the tranmission safe from the power available in the engine. Not that it's bad to pull out a little TM, just good to know.

As others mentioned, you could likely save some money on the stage kit to put towards that exhaust you'd like.