I recently changed the woofers in my Martin Logan Monoliths to Focal Audiom. Big improvement!! (I'm using an active cross-over, so I could get away with a change this dramatic). I found these used, so my cash risk was reasonable. If you go to Stereophile and look under links to die for there is a DIY section. You can find places that sell drivers there. I've also heard the Cabasse drivers are very good--but have no first hand experience with them.
