I've been reading up on this (or trying to) and I keep coming across explanations of Parametric EQs where the Q represents an exact range of frequencies rather than a general shape of a curve. One site even had an interactive Flash thingy where you could play with the gains, center frequency and Q value and the results would be shown in real time on a graph. No matter how high I boosted the gain, the beginning and ending frequencies were always the same. I've been trying for 30 minutes to find that link and I can't ... it was for a main stream car audio manufacturer that was demonstrating this feature on their mono-sub amp.