the other option instead of aftermarket is to install the factory cd button radio kex-m9071zt and the cdx-m9071zt cd changer . a cd changer cable would be needed also. then when cd button actuated the radio equailizer will turn on the amp under the passenger seat to full fidelity. on your present radio when fm button pushed the amp is only on low fidelity to avoid tape and fm hiss. by the time you change the amp and speakers going aftermarket the used factory system would be cheaper. with the factory system it is plug in and play which anyone could install. carstereohelp.com shows how to remove the radio to replace with a used cd button radio.

 

the above answer was in response in what to do about poor sound from fm modulated changer on a 92 es300.