Resource For 5th Gens (TSB's/Parts/Sites/Reviews) - Preludepower.com
look through the exhaust threads.
but yah not only do u need a badass exhaust.. u need headers, and probably also cams..
but i have a cai with an aem dryflow filter that filter denenitely added some depth to my exhaust tone.. and then i got the greddy evo.. car sounds awesome.. well still not as good as i want.. but ill get there.