I use fillet knives as well, i also use my hunting knife, my buck. There is nothing worse then having to sharpen your knife every other cut. A good quality knife is well worth it, I would spend the money any day then put up with a cheap knife that can't hold an edge! I think there's a huge difference in the metal quality in some knives. Sometimes finding the knive you want takes a while though. Once you've found it your set though!