what 4x6's and amp do i need?

I am looking to upgrade my system in my 1993 GMC pickup (ext cab).  I am just looking for some ideas on what a decent size amp i would need to run the front and back 4x6's, and what 4x6's are reccomended for this to sound clean and clear when it is turned up.  I am running a set of 4x6's off my Blaupunkt head unit, however the louder the volume to more distoriton there is.  I am basically looking to get rid of that.  Any help is appreciated.

 I recently bought some boss riot speaker's. I was very impressed at how well they sounded at high level's. For the amp It all depends on the rms of the speaker's you get try to get an amp with an rms about equall to all you're rms on you're speaker's. If you're going for high end stuff try Ma Audio, diamond, Mb quartz. For lower end stuff with legit power try Blaupunkt, lanzer, or low end mtx.

 Also most speaker's aren't made to hold a lot of base at high volumes.(they blow very easy} So if you got a lot of bass in you're speaker's and crank them up it tend's to distort almost any speaker you might get.......unless you go the component route.