I just installed a pioneer deh-p7700mp upgrading from a stock scion premium system, upgrading to my '' aftermarket '' pioneer it has drastically improved the sound. Now I'm wanting to add an amplifier. But the thing I don't know if I can put an amp on stock speakers. I'd like to buy new components, and rear speakers.. But I figured I can get a 5 ch amp and also have a subwoofer.