Finally finish doing preventive maintenance on my car (at least I think) -

Changed LIM Gasket/Elbows/Blower Gasket
Changed Supercharger oil
Changed Oil pan/gasket
Changed tranny fluid/gasket/filter
Changed Control arms
Changed both cv axles
Changed both tie rods

Now I am wondering what mods can help me reach my goal of about 350 whp or closest to that goal, my budget is around $2000.
One thing I am getting for sure is a new exhaust since the one currently on the car is loud in the middle (I think a leak) and rusted to hell.
Maybe brakes? I am not sure. What would you guys recommend? Not experienced at all with grand prixs but a friend of mine has experience with 3800s working on them for a couple of years now, he will be helping me install the parts.
ALSO I plan on keeping this car running for as long as I can, not really sure why, probably because its been my first and only car and has a lot of sentimental value haha, but my other question is. are there any good companies that sell upgraded transmissions? I want to get one thats been upgraded and will not have problems running that much horsepower and torque. Thanks in advance!