Better check out Flowmaster's site. There have been a few with older Malibu's who've installed Flowmaster muffler and been happy with the sound. If you don't want it too loud then look into the 80 series muffler, and if you want a clue as to how the 60 degree V6 engines sound with a Flowmaster look on YouTube for videos of Camaro's with the V6 or N-body GM's (97-03 Grand Am, Malibu, Alero) for sound clips.
If you want a deeper tone then go with 40 series flowmaster. If you want a mellow tone, stick with the 50 series. Had them when I had my v6 mustang and they sounded nice and didn't drown out the interior noise.