In case you're interested, this the 'official' Belanger muffler that comes with the kit
Dynomax 24219 - Dynomax Race Bullet Mufflers - JEGS
I think that's where the deeper rumble comes from. I bet it would achieve a similar deeper sound in a non-headered car as well. Like Warfangs TNT set up, or the Corsa,
I believe the muffler itself (and not the cat back piping) has a whole lot to do with the sound. The headers take it to a different level.
The cheapest way to experiment is to eliminate the rear muffler with a couple pieces of 2.5" pipe. Any muffler shop can do it. Put the stock tips back on. Cost around here for that job is currently about $45 bucks total. It may be more in the city, but my guy did the whole job in a 1/2 hour back in 2000. ....so time wise that's what we're talking for labor. It will definitely start you in the right direction for the sound you're trying to get to
i like it the way it is.
Steve