Stock sound systems have come a long ways, my 2500 has the 6 speaker while my 1500 had the 9 speaker with sub. I imagine the change from the 4 speaker to 6 would make a bigger difference, the imaging from the speakers on the dash would certainly make a huge difference.
There is a difference but it's honestly not that noticeable, and it's mostly in the very low end where the sub would take over.