The cheapest way to get sound @ minimal cost is a custom non-resonated midpipe. You will hear your car on throttle and turn on will be louder as well. Especially cold starts.
But to get opyimum sound. I would with a full exhaust set up. Intake, headers, exhaust, test pipe. Just like a v8 except you have less room to wwork and lacking some torque. The trade off. More agility, near flawless handling and tons upon tons of feedback.
