By the way, you might be underestimating the filter. Yes, it does remove a range of tones from each voice, but that is the basic principle of a subtractive synthesizer. You should not use it as a static frequency filter (allthough you can use it that way). Proper use of the filter involves dynamically adjusting the filter frequencies with the melody played, and altering the filter while a note is playing.
Take a look at these examples from Jeroen Tel:
In both examples the filter is not only used to generate alternative waveforms, but also to make smooth transitions between waveforms, i.e. in Cybernoid the waveform shifts from near perfect pulse to almost a sine wave.
Those smooth transitions have great musical possibilities.