Search around on this forum under the Parts for Sale thread- wait till someone sells a DC5 aftermarket exhaust (either Type R or Type S)
You can either go with a catback or full exhaust with headers.
Lot of people say dont go with full exhausts with header for a auto but Sky is the limit.

I waited around the forums and bought an 5zigen Proracer Exhaust catback with midpipe.
When i went to install it i had to change some of the piping as it came of a type R and didnt directly go onto my base model so thats a FYI.
Sounds deep and is pretty quiet toned as well i really love it.
Let me know how you go + goodluck!