I use 5 watts/ gallon rule as well. I have a rena excel 300 watt in my tank, a bit higher in price but my water is always where I want it. I have other brands as well I would not go with a hang over the top of tank heater. They usually dont have a setting to turn it to for temp, you have to mess with them to get them right, I do have about 10 of these however, cause they are so cheap.
If you want a good biowheel, and have some extra money, for 99 dollars you can get a Magnum 350 pro canister with a dual bio-wheel. Marineland makes this and the emporor. Your choice of a filter is not too bad either. If you decide in the future you want a lot of plants then you filter choice wont be a good one. The magnum 350 you just dont use the bio-wheel then.
They also have a Hot-magnum with Biowheel(hang on the back)for 65 dollars. It wont hold as much media as the 350, and 350 wont hold as much as a lot of other canisters but it always worked great for me.