first of all welcome to the boards. secondly, go to this site to listen to a wide variety of exhaust clips.
http://66.29.18.42/forums/index.php
here's my take on the options you've listed. each one has its own sound, with the stingers, LMII and Packs being similar. the flows will give you that older muscle car sound, as well as some drone. the other 3 will be loud, but not compared to if you had an o/r or hi-flo catted mid-pipe. take that into consideration for the future.
the loudest you will get with the stock H-pipe is the LMI's, and it will sound good too. BUT, when you finally get a mid-pipe, you may not like the sound too much, especially if you get an o/r X. i started with the LMI's and stock H, loved it. then went to a catted X, LOUD as hell, but too raspy for me. then LMII's. too quiet. then LMII's w/ O/R X-pipe. Just perfect!

it's LOUD, but not obnxious, it sounds real good and mean. similar to the Borla Stingers, but not quite as gurgly.
The stingers and packs are both great products. Stingers w/ o/r X is one of the best ive heard (of course bc its similar to what i have

). the packs are loud as well, but have a different, more racey sound than the packs or LMII's.
i highly suggest you think about what future mid-pipe you want to get, and use that to determine what exhaust to get. dont be impatient and have to have the loudest exhaust now, bc when you finally get that mid-pipe it will turn the sound of the car into a whole different beast. also, dont get the american thunder cat-back. just but some original 40's and have them welded in the stock tubing. save yourself some money. good luck deciding.
