I'll add my here. On a mildly built motor, Dynomax ultraflows would be faily quiet. But on a modified motor,they are quiet at idle but not at WOT. I love my ultraflows but with mine, x pipe installed, they are not quiet. In my mind, they are perfect. I love the sound, but quiet it really isn't. If you drive it like you stole it, you may want something else. Just trying to be fair here. I'd do mine the same all over again tho.
There have been threads with sound bytes previously. You may want to check the archives.