100 watts

hello, i am looking for ideas on how to design a police type 100W , 12V, power amplifier. the idea is that this amplifier can be installed in a 12V car and produce 100W R.M.S output through an external speaker. i know that it is not something special and that there are a lot of products...

http://rover.ebay.com/rover/1/711-53200-19255-0/1?icep_ff3=2&pub=5575378759&campid=5338273189&customid=&icep_item=143775964710&ipn=psmain&icep_vectorid=229466&kwid=902099&mtid=824&kw=lg&toolid=11111

Ok so im finally upgrading my stock speakers to alpine type r's. I am going to have 5.25 alpine speakers in the front and type r 6x9's in the back. the 5.25 rms at 90 watts and the 6x9 rms at 100 watts. my question is do i need to get a 4 channel amp that RMS's at atleast 100 watts per channel...