i hope you can learn from my error.....i had dumped spintech mufflers...just before the axle and the dumps were clocked at 5 on the pass side and 7 on the drivers side. with no interior....man, that was loud, rattley and droney....i just added tailpipes to the rear and it's night and day.
so, i don't know what kind of motor you have, but i've heard some nice mellow magnaflows and turbos. my system is 2.5" & x-piped.....low rumble at idle, but really comes alive when you stomp on it.