You can either replace the bose amp or not....that's up to you. But you will get better sound quality with a different amp. 200 watts is also not much to run a whole car, especially if you want a good sized sub. I have a small 8" JL W7 sub, and 300 watts is considered optimal power just for that. I ran my 2 component sets off the Bose amps for a few weeks, and it worked OK, but adding a pair of 300 watt amps made a huge improvement.