My stereo Eurovox system has not much power and the speakers have been designed to throw out treble from the 2 tiny front dash tweeters, midrange in the front door and back door speakers and almost muffled sounds considered to be flat bass from the rear dash speakers. Is something wrong or were they supposed to act in this way? I want to upgrade to better sound by changing speakers only at low cost, brand is not important, but finding the right sizes to fit is critical and mounting simplicity is required. I do not wish to cut away metal or trim, do the old speakers come out easily without removing the door panels and new ones fit straight in with screws only?