Upgrading stereo system

[Big-T]

The easiest way to upgrade the sound of most factory sound systems is to add bass. You'll be amazed at how much better the entire system appears to sound just by adding bass. That's the VERY first item you should ever consider before thinking about anything else. For most people that will be sufficient to satisfy any urges for quality sound.

I'm not familiar with the Mustang system, but I'd say you just tap into the rear speakers with an LOC to an aftermarket amp and subwoofer in a box.

T.