Get exhaust for sound. T1R Sparrow exhaust!!! Also, an intake to enhance sound further. I've got a Comptech CAI, and it sounds great!

 

I'd start with the basics like intake and exhaust first just to free the engine up and gain some nice mechanical music.

Here is my mod path so far:
intake
x-brace
catback exhaust
testpipe

future mod path:
full coilovers
4.56 gears
boost