Performance

I just got a 2003 Altima 3.5 SE 5spd, black leather, bose in dash 6 disc. I love the car. its awesome. I need some reccommendations on what I should do to it. The stereo is pretty good, so I dont' really need to change that, at least for now. I would really like to up the power a little. What should I do to get the best power for my buck, intake, exhaust, etc? Previously, I owned a 350 V8 silverado and I loved that dam thing, can't beat the torque. Exhaust on a V8 is simple, Flowmaster. I had to get rid of it cuz of gas. But now with this car there are a lot more options for perfomance. someone please help me Ryan