It is extraordinarily difficult to set any equalizer just by listening. . . you may be able to get broad ranges of frequencies balanced, but that's it. What I do is play pink noise (ripped to mp3) from my Rio Car, then use RTA (real-time analyzer) software on my laptop with an external microphone to evaluate frequency response. I can visually see what frequency ranges need correction, and the beauty of a parametric equalizer is that I can adjust the freq, boost/cut, and Q. I don't own a calibrated microphone, so what I do is get a baseline freq vs. amplitude graph from a pair of reference speakers in my apartment first. The result is absolutely superb, but obviously not as good as my reference system. This method will work with any car system, but preferably if you have some quality aftermarket components installed. Alternatively, you can just take your system to a high-end roadshop and ask if you can play with their real time analyzer equipment (might cost you $$$, but worth it). Good luck!