Zoomers do sound great on the Challenger SRT. Zoomer exhaust is a company in Irvine, CA that is run by Dave Arlasky who built and raced top fuel Funny Cars and Dragsters back in the 1960s and 1970s. Here is their web site:
Zoomers Exhaust Works - Performance Exhaust Systems, Exhaust Tips, and Cat-backs
Also, here is a comparison clip of Zoomers on a Dodge Charger R/T. They sound good with the 5.7 but don't growl like the 6.1.