Part of it might be EQ settings in the HU but another part is that the front speakers are better quality 6.5" while the rears are cheaper 5.25" drivers. If you like more sound behind you, you can try changing SSP and fader settings but the best solution is to replace the speakers.
Personally I like my soundstage in front with just sound fill from behind so I like the stock setup.
I am so used to having the sound stage in the back, old setup with kickin 6x9s, that the stereo doesn't sound right to me no matter how I adjust it. I am considering adding some 6x9s to the back pillars in the distant future.
I love the sound of a good set of 6x9 speakers! I still miss my 3-way Kappa 6x9 home-made boxes that were stolen from my Nissan truck many years ago. Even though the soundstage was all wrong, being behind me, they sounded so sweet and I didn't even need a sub.
