The first thing to keep in mind is that the subwoofer amplifier gets its signal from the rear speaker outputs. So if you turn down the rear speakers you are turning down the sub as well - check the fader. The ideal fix for this would be to add a sub under a front seat, driven from the front speakers, but for most of us this would be overkill.
I assume you have adjusted the equalizer, but it bears mentioning. There have been mentions in other threads of a setting to check, but since I have a base model it doesn't apply. Try a search...
Contrary to a previous post, I find the stock ELS speakers to be inadequate entry-level OEM speakers - and I have had every one of the basic ELS speakers in my hands, as well as listened to them. By replacing the speakers with quality aftermarket parts you will find a noticeable improvement to the sound. There are a number of threads on the bass response, and replacing the subwoofer, so look around. Also, keep in mind that the sub is only working with frequencies below 200kHz or so, and much of your sensation of the bass is from the door speakers (which are inadequate IMHO). If interested in upgrading the speakers, either yourself or at a shop, read this thread:
http://www.mdxers.org/forums/94-thi...acing-front-speakers-components-wiring-4.html . Be patient, as we chased a few dead ends on the way, but if you read to the end you will see what is involved. Spending a few hundred dollars to upgrade the sound on a +/-50k car is well worth it.
For those who want to do some analytical work, download an audio spectrum analyzer app for your phone and a pink noise mp3 file. While playing the mp3 file look at the frequency response in various positions around the car and next to each speaker. With the new speakers the sound looks pretty flat, with a boost in the 1kHz-3kHz mid-range and a notch at about 10kHz (perhaps reducing interference?). With the upgraded front door speakers the bass there rolls off between 70Hz-60Hz, which is very nice. The rear doors roll off below 200Hz as a result of the sub crossover. The upgraded sub is delivering down to 35Hz. It would be interesting to see the results of similar testing on the stock speakers.
Greg