hey, i got some 2.5" twins n it sounds fine, however i spent like $200 on a hi performance muff.
before i had a str8 4" cannon. = i couldnt hear anyone inside the car whilst driving.
NAs are alot louda than FIs id so if you like the big 3" i sujest a gd muffla = still sounds sporty and you can hear the cd player playn aswell