I'm sorry, but no software is going to overcome a hardware limitation, especially on Speakers.
I guess software can kinda speed up a slow processor or low RAM, but it cannot boost the power of an amplifier or the frequency response of crappy speakers.
The only thing I'd say to try is maybe using the Graphic Equalizer that came with the soundcard drivers (if there is one) and try to tweak that. Other than that.... I'm outta ideas... Sorry.