I just bought a 98 Bonneville SE with 59,000 miles, and want to Upgrade the stereo.

It has the factory Theft Lock CD with EQ in the dash.

I already have a Boston Accoustics 12.5 Pro Subwoofer in a 1 cubic foot box, and some Sony 6x9 explodes (the silver higher end ones ) from my old car as well.

Should I add an amp and replace the backs and be done with it
BTW what'* a good quality relatively inexpensive 200 - 700 W sub amp theses days.

or should I get a new Alpine CD105 head unit and replace the factory stereo

Also what is the max size door speakers fit I have the ones with two holes
do the Polk db6501 fit in this door.

Thanks in advance.

Stock is stock. I have heard some really nice cars before that kept the factory deck, but uprgraded everything else.
Get rid of the old paper cone speakers and upgrade them and toss an amp in to feed the hungry puppies.
Black_Friday is our audio Gearhead. He can let you know what will work great in your car.