Hmmm...tough call. What sounds good to some don't sound good to someone else. It's a pretty subjective decision.
However, it depends on what you want. Flowmaster sounds great as does Magnaflow. I prefer the Magnaflow sound but that's a personal choice.
Gibson sounds really good but they are dang expensive.
I suggest you go to some of the mfgr's websites. Most of them have sound clips of their systems on your vehicle.
Here's a link to the Magnaflow site and their vids for the HEMI powered Dodge trucks:
Here's a system from Flowmaster that will fit your truck:
I'd poke around a bit on the Flowmaster site to see if they have any video or sound clips.
And check out our local vendors here when you pick one. They have some great deals!