I have the pioneer 4x10's also. Sound pretty good, hooked up to my Alpine V12 amp. Of course I have the x-over turned so the 4x10's won't get anything under 120Hz. If you want bass, get a sub and forget about the 6x9's.
The best sounding speakers I've heard, was a pair of 4x10's in the dash of my friends fiero paired with a cheap pyramid amp. That and the single 8" sub was the best sounding system I had heard! (Most likely the very small interior space had something to do with it, but that thing was extremely clear and would hurt your ears)