fitting
What you have to think about mostly is the mounting DEPTH rather than actualk size of the speaker. Rockford Fosgate over sizes all of thier speakers both width and depth. I have had many problems before with Rockford speakers hitting cutomers window tracks and being too big for the mounting hole. your only hope to try it out, but i think you may have trouble getting those rockfords to fit. Infinity may be more along the size of the Rockford speakers, depending on if they are Kappa or Reference series. I would only use the 3 inchers in the dash if you plan on using them as a tweeter, and not as a full range speaker with a seperate tweeter. If you cross over those 3 inch speakers and use them as all highs you get a great sound stage. 6X9's wont fit in the rear unless you use adapter plates, and those almost never fit right, wich defeats the purpose of having them. I just have 4X10's, and a sub to fill in the bass, and its all balanced pretty well. remember that your not supposed to actually HEAR rear speakers over the fronts, they are just in there for filler so its all ballanced. Pioneer speakesr fit in everything, so do kenwood dual mags, they have VERY small magnets, and still crank in the sound.