Oh man it took me ages to get things right when it comes to exhaust.
It took two mufflers & 2 "hot dogs" to get mine to sound the way I like it, ie minimal reverberation, deep but not excessively loud to wake up the entire hood when on the gas.
Firstly I removed the stock exhaust & manifold & fitted extractors or headers as the US guys like to call em. Cost & $180.00, (Note; be prepared to make up some silly washers to clamp down on some of the extractors out there, I had to do this. From memory you did the same with prior last 260, Nate!?).
Next was 2.25 inch pipe straight through larger size hot dog to big ricey "muffler" which a small cat could quite easily have crawled into. big mistake! way too loud and lost all bottom end power with a head splitting reverberation at about 2500 rpm.
Solved the probem by reducing the hot dog and changing the muffler to what I think was called a "TURBO FLOW" muffler with a 2.5" dumper which also helped reduce fumes entering the car from rear which is still a slight problem I'm trying to fix!
I think all up the correct set up for me costed about $550.00, but the sound is just right especially at idle and also when openned up down the street. hmmm...I've got a lot of growing up to do! hehehe
Cheers
Sulio