When I had my 01 SS Camaro I was looking for a very mellow tone at idle with a very mellow tone at WOT with the cut outs closed. What I ended up doing was:
Long tube headers
Dual electric cut outs right off the collector
3" to 2.5" reducers on the non cut out side
Dual Catco cheap cat's
2.5" dual to single 3" flowmaster y collector
Single 3" in Hooker Aerochamber muffler with the factory dual 2.5" tips out.
(forgot how good it sounded until I found the sound clip:
http://73-ls1.com/misc/Thunder236.wav )
Thing sounded close to stock as far as tone and how loud it was. You would have to listen to hear the big 236/230 .595/.575 lift cam in it. Then, on race day, open the cut outs and it was one loud car.
My truck is pretty deafening right now with
3.5" collectors down to 3"
3" X-pipe
Warlock mufflers with Dual electric cut outs hung on the muffler
No dumps
It was louder with the plugs they give you for the muffler as they have an angle to them, but with the flat portion of the cut out, it deadens the sound some.
I'm planing on getting rid of this set up and going with:
3.5" to 3" reducers
Dual electric cut outs
3" to 2.5" reducers
Dual 2.5" in / Single 3" out Hooker Aero Chamber Muffler
Dump just before the rear tire on the passanger side.
If this isn't quiet enough, I'll put something between the out put of the muffler and the dump.
I don't need the noise or the performance when capped. It will move plenty for around town even with a big plug in it.