I have a friend who used chambered exhaust on his Camaro BBC ..... he ran the exhaust pipe all the way back exiting in the stock position under the rear bumper.
It had a nice mellow sound..... not as loud as one would expect from a long piece of pipe with no restriction or baffling inside..... with only dimpling from the outside to tone-down/mellow the exhaust note. I assume the powersticks are similar in design.
I used the "shorty Summit" muffler and was surprised how LOUD they are. Not much bigger in diameter than a tail pipe ..... so it you're looking for loud.....
go to: http://www.summitracing.com/parts/sum-630810