Mainsound, to answer your question about whether an equalizer will help: USUALLY it won't. An equalizer can only be used to cut peaks in the bass response. It can not be used to boost bass response.
If you were complaining of too much bass, or boomy bass, or one note bass - then an equalizer would help.
Insufficient bass is caused by a limitation in your amp, or a limitation of your speakers, or a problem with your room (e.g. if you are sitting in a null). Think about what would happen if you were to boost the bass. If your amp already struggles to deliver bass, boosting bass would cause it to clip. If it were a problem with your speakers, boosting bass would cause excessive cone movement and introduce breakup modes. If it were a problem with your room, no amount of boost will overcome the cancellation of bass at the listening position - whilst at the same time you are drawing more amplifier and making your speakers work harder.
HOWEVER, in your case, you are kind of implying that your subwoofers are not level matched to your main speakers - at least that is what I read into your statement "This system is capable of putting out the bass when the music is called to do so, but often I would like to hear a little more bass in general. There are no bass or treble controls".
If this were the case, then you need a device which would be able to level match the main speakers and the sub. You can either attenuate the main speakers, or boost signal to the sub. An equalizer should be able to do this, provided it is capable of amplifying the signal beyond unity gain. However, it would be better to use an active crossover.