undergravel filters are better for salt water tanks due to the incredibly difficult water cycles the tank has to go through.. i'd stick with the power filters (back hangers) if it was for fresh water...the water cycle is shorter and once you get good biological build up on the power filter you are all set. if you want the best filter find yourself a magnum... they are old school but work wonders. hell, i dont even know if they make them anymore... i used to work at a fish store, fun times... fun times...
100 for a 50 and hood isnt too bad actually, providing its a flourescent hood.. if its incandescent you are getting raped hard.