Aftermarket Speaker Installation

I've been wanting to get some new rear speakers for my '01 Grand Am because they have completely rotted out from sun damage. I've found the 6x9 speakers I want from Crutchfield.com but it says I'll have buy a new radio deck and bypass the factory amp by cutting and splicing into the factory wire harness since I still have the factory radio. Has anybody done this and if so how difficult would it be? I have friends that have aftermarket speakers with factory radios so I want to know if there is anyway to get around this. Thanks

You can install aftermarket speaks in the rear its just a little sketchy. Thier are 4 wires that goto each rear speaker.
One set carries the bass freq. and the other carries the highs.

What I did was removed the tweeters from the factory speakers(1 philips screw holds them to the speakers) and attach those to the high leads , then affixed them under the factory grills.Then connect the bass leads to the speaker.

Also the only way(and easiest) to get 6x9s installed is to use the black frames the stockers are in. Just break the tabs off the edge of the frame and it'll fit good.

>> Edit>>
Ok I have a couple that might help.

http://i28.photobucket.com/albums/c242/xeroinfinity/N%20Body%20Dash%20Removal/DSCspeaker188.jpg

http://i28.photobucket.com/albums/c242/xeroinfinity/N%20Body%20Dash%20Removal/DSCspeaker185.jpg