Its completely a matter of opinion, I'm a flowmaster guy and will be putting their cat back setup on my car whenever it gets here and they do have the Hushpower series, but I've heard some really good sounding exhaust from JBA, their competition series, its pretty aggressive though probably not what you're looking for.
2011 Synergy Green Metallic 1SS Camaro:
RS Package, White Ralley Stripes, Premium Sound.
Mods; Flowmaster Exhaust, Vararam CAI, Pfadt Sport Suspension, Budnik "Ice" Wheels, Nitto Invo tires
Upcoming Mods; Custom grill and badging.