Amplified properly, ie with the Pioneer D3 and not with the weak stock headunit, the four speakers will sound pretty darn good. I would also add a subwoofer with its own amplifier for better bass response, and I really don't think you will be able to get much better by adding more speakers. The issue with the basic system, and even the sound package, is not the number of speakers; it's the lack of power (RMS watts); that's why those who upgrade to the D3 report much better sound; the D3 features Pioneer Premiere MOS-FET amplifiers.

Even if you don't want to change headunits though, it's pretty easy to reamplify the basic system 4 speaker; add a basic 2- channel amplifier with line-level inputs and splice it into the speaker cables leaving the headunit so it flattens and then re-amplifies the signal before it hits the speakers.

- Suneet

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- Suneet