stereo problems

I tried to install 2 /10 inch Hollywood speaker and a 400w amp, unfortunatly, everytime I would turn off the cd player or hit the brakes, I would get a very loud feedback noise (loud and low vibrating noise). I wondered if this was because I stayed with the original Bose head unit that included a cd player and tape deck. Is there some type of special adapter or power boost I could get for the original head unit, or would I have to go with a more powerful cd head unit?