Pioneer Sound System Upgrades

[osylith]

I was wondering if anyone has upgraded their sounds systems with an amp. I was going to put an amp in. I was wondering if the amp from the factory is the best for the speakers in the car, and should I replace the speakers at the same time. Also the sound is good, but i just want better bass the highs are pretty good, but sometimes on rap the bass gets distorted with the settings higher. So if i just installed a amp for the bass would that fix that?