I was blown away with the difference when i first heard the new speakers for the first time, HUGE difference in sound volume and quality, that was my biggest notice with them.
All i did was have the factory speakers in the corners of the dash replaced with the Kickers and also went from the factory 4x10 in the rear side panels to a Kicker 2-way 6x9, the guy made a carpeted adapter plate to keep a clean look, and had to widen the opening alittle for them to fit, but it's very clean install and extremely much better sounding than what i have ever had in there.
Then of course, add in the 2 - 15" Kicker Comp VR's in there, it can get alittle loud
My goal for this setup was not to go TOO overboard, but have as much of the system as hidden as possible, or in factory locations, aside from the coffin of a box in the back behind the seat.
I'm happy with it though.
Lots of babbling on here, sorry, but really i personally believe you would be very happy with a simple aftermarket, higher quality speaker replacement in the factory dash locations, at the corners.