I think it will really depend on the kind of fish you will be putting in your tank, and what the bio load will be. I have 5 adult angels and a 4 inch pleco in my 55, and only have sponge filters in that tank. If you are gonna load it down with african cichlids where your tank will be basically overstocked, the fluval might be the better choice. If you are considering getting a canister filter (fluval), also look in the other canisters available. I am partial to the filstar XP canisters, and they are a little cheaper (I think) than the fluvals. Compare the gallons per hour, price, is it self priming, and does it include media when doing your research.
As far as the heater, I think I would get a new one, and I would get 2 for that tank. One heater on each side will ensure more uniformity in the tank, and help eliminate cold spots. Also, if one of the filters quits on you, the other one will take up the slack until you realize what happened and replace it. You should consider 5 watts per gallon, so your tank needs about 525 watts. I have a little overkill in my tank and have 600 watts (300 each) in my tank. Also, look into getting a stainless steel or titanium heater. They cost about the same, and you don't have to worry about breaking them.