well, there is a few things you can do. first, iether high flow or no cats will deapen the tone some. headers will help as well. as for dueling it out, i would sugest an x-pipe where the y pipe is and go with flowmaster 40's. i have them and they have a different sound than otehr mufflers on a 6. another way to go though is glass packs. they will have the glass pack pop, but people will hear you from a mile away. one that i just recently found are warlocks.
here is a sound bite of a 95 6 with warlocks.
http://www.mustangexhaust.com/sounds...aders,00V6.mp3
all in all, it comes down to personal taste. check out
http://www.3.8mustang.com/ on their forums, they have a sound bytes area some where in the bolt ons section, and knowlegable people who know quite a bit about v6 mustangs.