There are 2 popular tuners for the Hemi. The Diablo Sport Predator and the SuperChips Cortex. There is some great info in the Mod Zone in the 5.7 Hemi V8 Performance section. Here's a link - http://www.ramforumz.com/forumdisplay.php?f=83
It's a big section.....over 3500 threads!
Do NOT buy that chip, its a total waste. Your going to have to spend 300$ and 200 if you can find a deal. Get a Superchips Flashpaq 3845 I believe, could be wrong on the number just need the newest model. i have the 08 4.7L and it woke my truck up and its a beast, my buddy has the exact same truck as you, 2008 5.7L hemi and got the chip and he didnt notice much. Just my opinion and my 4.7 now smokes his 5.7