Anyone upgrade their interior and exterior speakers?

I'm a huge Polk fan, so i'm in. I need to measure mine - i guess my question was more about size. Without measuring, it seems like the speakers are around 4".. which, i believe the only aftermarket replacement that i know of would be the 3.5's..

Those that have added an amp.. Where did you find the speaker lines to wire to? I'm interested in this, have a few 4-channel amps laying around..