If you don't have a tank yet then I would be looking one for one that has a built in overflow. The tank you are describing has a filter system that hangs on the back of the tank. This is similar to all those little freshwater tanks we've seen in people's houses. The filter system is a small plastic box that hangs on the back and has filter pads and possibly a spinning paper wheel that is supposed to act as a biological filter.These are really insufficient for a reef system. The water in a reef has to be pristine. You need far more biological filtration than a little wheel can provide hanging on the back of your tank.
I would recommend a tank that has a built in overflow. This is basically a hole drilled in the bottom of the tank with a tube coming out of it. The tube and hole sit behind a plastic dam. Water from the tank spills over the dam and then goes into the tube and out of your tank. You hook up some plumbing to the outlet of the tube and run it into a sump system. This is basically a group of plexiglas boxes which are big enough to house larger filtration components such as wet/dry filters, skimmers and refugiums.
The advantage of a sump is that you can have larger pumps, larger skimmers and more overall filtration and you can put it all either under the tank or in another room. This keeps it out of sight and keeps the noise down. I have my sump mounted in a room behind my tank. I passed the plumbing through a hole I cut in the wall behind the tank. All the pumps are in the sump room, including the heater. This makes the tank completely quiet and keeps wires and things out of my main display tank. It also gives me more room to work on things such as cleaning out my prefilter pads.
Since you are just starting. I would look for a tank with an overflow first. After that, then we can recommend a sump system. Some tanks come with a sump. For a reef you will want at least a skimmer and a main pump which is big enough to turn over your entire tank's volume of water at least 10-15 times per hour. There are other options such as ozone, ultraviolet, live plants in a refugium, wet/dry filters, and canister filters that have activated carbon in them...
