yeah, i think a lot of these 'rules' apply more to general music recording, where you are using mainly sounds fresh from thier source whatever that may be and just trying to lock them togethor neatly..
In techno you are trying to create a whole different sound so you have to figure what works for you. as long as you can get a decent well balanced sound overall you can throw away the rulebook.

Mark is right too, next time you want to boost a freq, try cutting the other freqs instead..

re. polishing a turd.. i do this loads, sometimes i hear a sound thats crap but there is just a faint slither of somthing cool hidden within, sometimes ill use several eqs layered up to get the tone im looking for out of it.