[alpine25]

Well if you keep the factory stereo, you will need a line out converter, splice it into the rear 6x9's. The thing about an aftermarket headunit is that you will have a high pass and low pass filters. This reduces the bass to the front speakers and sends it to the subs. You would also not need the line out converter with the aftermarket, as there will be rca outs on the deck. When i had my factory speakers in my car, they sounded a good bit better after i put the new headunit in. Why not try the install yourself? Its not that hard besides the power wire to the amp.