if you are concerned about the sound, you should be able find some sound waves for 40 series, 50 series and super 44's.
I have personally always liked the Flowmaster sound and have had them before on a 4.6 2V (non PI). It was on a Thunderbird and the Force II cat back was the only option available at the time from Flowmaster (these used the Delta 50 series mufflers). Though it did offer an improved tone over stock, I recall not being happy till with the tone, until I installed my JBA headers and made a custom "true dual" off road midpipe for the car (then it finally sounded like I wanted it to).
For the 02 GT conv. that I just got, I have yet to change the exhaust (will be doing very soon).
At first I looked to just swap the mufflers to the Super 44's and leave the rest stock. (I was however unsure if it would give me the rumble I truly wanted). I personally have heard and decided to leave the factory cat-back and only swap the mid-pipe with an off road H-pipe. (this will also allow me to change it back to stock without taking it to a shop).
But to each their own. I do feel that Flowmaster offers a good variance in sound via their different series. Have fun, and hope you find the perfect tone you are after.