I clean about 200 walleyes, and 500 perch a year with this American Angler, and it's on its 3rd year now, same blade, never had to sharpen, even with big walleye ribs that I cut right through at the back-bone.
I actually bought the big set, but I never even tried any of the extra blades, no need to, so I would recommend the single blade knife. You can order extra blades if needed...
http://www.amazon.com/American-Angler-Electric-Fillet-Freshwater/dp/B00CWX4JTG