Bypassing the stock amp is trivially simple, and the amp is only rated around 7 Watts RMS, 10 Watts peak per channel. Any new CD player/tuner you buy will be significantly more powerful.
I installed a Blaupunkt Miami (or was it Denver? - I forgot already!) at 35 Watts/channel peak - what a difference. All you need to do is to fab a cable for the 4 speaker output pairs from the radio, run it to the location of the factory amp, and connect it to the wires which go to the speaker locations. You'll need 4 Euro female connectors to plug into the male connectors located at the factory amp.
I ordered my radio from Crutchfield and they sent along one pair of connectors with the radio, so I called them and got another set. These connectors are cylindrical plastic, about 3/8" dia by 3/4" long, with a 2-wire pigtail coming out. I used crimp connectors to attach these to a longer pair of wires which I then crimp connected to the pigtail coming from the connector supplied with the radio. I did this for all 4 speaker wires, and then used electrical tape to bundle them together and ran the bundle under the carpet, from the radio to the factory amp location.
Steve - 87S4/auto/GPW
928 Tips Home Greg's Home