Could you post the measurements of your tanks for us please?
As for the airstone question - it really depends what you want to put in the tank. Some fish need a more oxygen concentrated environment and others don't. Some prefer more water movement(which the airstone would provide), some like the water as currentless as possible. So that said, after you figure out what you want, there should be plenty of time to decide if you need the airstone. The filter is a must though and I like the
HOB (hang-on-back) best. There are are others who prefer canisters. It's all a matter of preference. So you should be fine with the filter you have.
Carol