apexi ws comes to mind... quiet and stock looking but all the performance gains from aftermarket equipment.
i think its the WS it should be their cheaper line. (go figure

)
yeah its the World Sport (WS) heres a link
http://www.apexi-usa.com/exhausts_ws.asp
ive looked around on the web and most places are charging about 350-450 for the cat-back WS. retail is like 600 bucks so unless you've got pals at a speed shop, i'd suggest getting it online and either installing it yourself or have a shop put it on for ya.